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Hosseini, S. ,
Landrani, A. ,
Moghadam, M. ,
Sun, Y. ,
Tangestaninejad, S. ,
Mirkhani, V. ,
Mohammadpoor-baltok, I. ,
Karimi-maleh, H. ,
Mozaffari, M. Energy and Fuels (08870624) 39(24)pp. 11782-11792
Plasma catalysis for CO2 utilization technology shows considerable promise for advancement, with enhancing the synergistic relationship between plasma and catalysts being a key area of research challenge. However, current research focuses on the design of efficient catalyst formulations, but studies on metal-organic framework (MOF) screening and cold plasma methods have received less attention. Therefore, in this study, the hydrogenation of CO2 at ambient temperature and pressure was investigated using single-metal and bimetallic ZIF-67 as a MOF catalyst with the assistance of a dielectric barrier discharge (DBD) plasma reactor. The Co ZIF-67 and Ni Co ZIF-67 were synthesized and characterized by different analytical techniques. The synergistic effects between DBD plasma and these mono- and bimetal MOFs were investigated for the transformation protocol of CO2 to methanol. The flow rate of gas and input voltage as main parameters were screened. In this procedure, monometallic and bimetallic ZIF-67 showed 69.6 and 90.3% conversion with 84.1 and 98.1% selectivity of CH3OH production and 2.7 and 4.8 (mmol/kJ) energy efficiency under optimized conditions (flow rate: 60 mL/min; input voltage: 10 kV). Besides, the specific input energy of the transformation as a kinetic parameter was measured and showed linear behavior. The two catalysts can be reused up to six times without significant loss of their catalytic activities. © 2025 American Chemical Society.
Scientific Reports (20452322) 14(1)
In this study, entanglement of composition, additive and/or sintering conditions and their effects on magnetic properties of soft ferrites, nickel zinc spinel ferrites (Ni1−xZnxFe2O4, x = 0.65 and 0.70) which were prepared via conventional solid-state reaction method investigated. Also an equiponderant calcined mixture of Bi2O3, CaO, CeO2, SiO2, Al2O3, Y2O3 and nanotitania was mixed thoroughly and used as a multi-compound calcined additive (MCCA). Calcined ferrite powders were crushed, dry and wet milled, dried, mixed with different amounts of MCCA (0.0, 0.5, 1.0, 1.5 and 2.0 wt%), formed in toroidal shapes and finally sintered at different temperatures, from 1150 up to 1360 °C for 3 h. X-ray diffraction assessment confirmed formation of the single phase cubic spinel structures. Initial permeability and Q-factor spectra of the toroids were obtained from 0.1 to 1000 kHz, using an LCR meter. The results show that initial permeability of each sample has a maximum and addition of MCCA to the ferrites leads to a marvelous increase in permeabilities. Additionally, MCCA decreases the optimum sintering temperature too. The optimum amounts of additive were 1.0 and 0.5 wt% for the x = 0.65 (μ′ = 492, Ts = 1280 °C) and x = 0.70 (μ′ = 478, Ts = 1320 °C), respectively. Permeability spectra illustrate that utility zone of the Ni0.35Zn0.65Fe2O4 and Ni0.3Zn0.7Fe2O4 are both less than 100 and 10 kHz, respectively. The results represent that there is a strong entanglement between composition, additive and/or sintering conditions. It can be concluded the MCCA added Ni0.35Zn0.65Fe2O4, is suitable for application in the switching power supplies. © The Author(s) 2024.
Asgarian, S.M. ,
Mahjour-shafiei, M. ,
Mozaffari, M. ,
Shatooti s., S. Journal of Alloys and Compounds (09258388) 986
Single phase Zn2+-substituted magnetite nanocrystallites are synthesized via co-precipitation method and used as lithium-ion battery electrodes. The structural properties and vacancy distribution of nanoparticles are evaluated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and positron annihilation lifetime spectroscopy (PALS). The Rietveld refinement of the X-ray diffraction patterns shows that the lattice constant increases with Zn2+ content from 8.392 Å for magnetite to 8.448 Å for Zn0.2Fe2.8O4. The XPS measurements show that cation vacancies increase with Zn content on the surface of nanoparticles. Positron annihilation lifetime spectra suggest more concentration of monovacancies and larger size of vacancy clusters in the Zn0.1Fe2.9O4 sample compared with the other two samples, Fe3O4 and Zn0.2Fe2.8O4. Electrochemical measurements show better reversibility, higher initial discharge capacity, and lower electrochemical impedance for the Zn0.1Fe2.9O4 electrode, which are attributed to the higher concentration of vacancy defects in its nanocrystallites. The electrochemical impedance spectroscopy (EIS) shows that the Li+ diffusion coefficient (DLi+) increases with Zn2+ doping from 1.51 × 10–15 cm2s–1 for Fe3O4 to 3.25 × 10–13 cm2s–1 for Zn0.1Fe2.9O4, and 1.43 × 10–13 cm2s–1 for Zn0.2Fe2.8O4. The initial discharge capacities of the samples found to be about 1345.04 mAh g−1 for Fe3O4, 1435.82 mAh g−1 for Zn0.1Fe2.9O4, and 1063.72 mAh g−1 for Zn0.2Fe2.8O4 electrodes, respectively. During first few cycles, the discharge capacity decline faster as Zn content increases. The discharge capacity of the Zn0.2Fe2.8O4 electrode is stable at 410 mAhg−1 from the 60th to the 200th cycle, which is higher than the Fe3O4 electrode (150 mAhg−1) and the Zn0.1Fe2.9O4 electrode (270 mAhg−1). This variance is explained by the cation vacancy concentration and the lattice constant of the samples. The impedance of the electrodes is also affected by the vacancy defects formed during the sample preparation. © 2024 Elsevier B.V.
Physics of Metals and Metallography (0031918X) 125(Suppl 1)
Abstract: A unique intermetallic alloy composed of Fe (81–85 wt %), Si (7–13 wt %), and Al (4–7 wt %) which is named Sendust, is typically synthesized by conventional methods, such as crushing and/or atomizing. Various techniques have been described for obtaining Sendust nanostructures in recent decades. This paper reviews the synthesis, crystal structure, magnetic properties, and old and new applications of Sendust. Formation of its ordered and/or disordered phases through different methods such as mechanical alloying, atomizing, and/or melting is possible. Its special magnetic properties, including high permeability, low hysteresis loss, zero magnetostriction, and nearly zero first constant of magnetic anisotropy, make it suitable for a wide range of electronic applications. Various applications of Sendust from magnetic cores in power supplies, its role in magnetic recording devices, the excellent magnetic permeability of its nanostructures in the GHz frequency range, reduced power losses for suppressing microwave absorption, and electromagnetic interference shielding are reviewed. © Pleiades Publishing, Ltd. 2024.
Saeidi, Hamidreza ,
Mozaffari, Morteza ,
Ilbey, Serhat ,
Asanjarani, Neda ,
Saeidi, H. ,
Mozaffari, M. ,
Ilbey, S. ,
Dutz s., ,
Zahn d., ,
Azimi gandomani, G. ,
Bock, M. Nanomaterials (20794991) 13(2)
Magnetic nanoparticles (MNPs) have been widely applied as magnetic resonance imaging (MRI) contrast agents. MNPs offer significant contrast improvements in MRI through their tunable relaxivities, but to apply them as clinical contrast agents effectively, they should exhibit a high saturation magnetization, good colloidal stability and sufficient biocompatibility. In this work, we present a detailed description of the synthesis and the characterizations of europium-substituted Mn-Zn ferrite (Mn0.6Zn0.4EuxFe2-xO4, x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, and 0.15, herein named MZF for x = 0.00 and EuMZF for others). MNPs were synthesized by the coprecipitation method and subsequent hydrothermal treatment, coated with citric acid (CA) or pluronic F127 (PF-127) and finally characterized by X-ray Diffraction (XRD), Inductively Coupled Plasma (ICP), Vibrating Sample Magnetometry (VSM), Fourier-Transform Infrared (FTIR), Dynamic Light Scattering (DLS) and MRI Relaxometry at 3T methods. The XRD studies revealed that all main diffraction peaks are matched with the spinel structure very well, so they are nearly single phase. Furthermore, XRD study showed that, although there are no significant changes in lattice constants, crystallite sizes are affected by europium substitution significantly. Room-temperature magnetometry showed that, in addition to coercivity, both saturation and remnant magnetizations decrease with increasing europium substitution and coating with pluronic F127. FTIR study confirmed the presence of citric acid and poloxamer (pluronic F127) coatings on the surface of the nanoparticles. Relaxometry measurements illustrated that, although the europium-free sample is an excellent negative contrast agent with a high r(2) relaxivity, it does not show a positive contrast enhancement as the concentration of nanoparticles increases. By increasing the europium to x = 0.15, r(1) relaxivity increased significantly. On the contrary, europium substitution decreased r(2) relaxivity due to a reduction in saturation magnetization. The ratio of r(2)/r(1) decreased from 152 for the europium-free sample to 11.2 for x = 0.15, which indicates that Mn0.6Zn0.4Eu0.15Fe1.85O4 is a suitable candidate for dual-mode MRI contrast agent potentially. The samples with citric acid coating had higher r(1) and lower r(2) relaxivities than those of pluronic F127-coated samples.
Journal Of Chemistry (20909071) 2023
Tea waste was used to successfully synthesize magnetic nanoparticles (TWMNPs). In this investigation, Pb (II) was eliminated by tea waste modified with magnetite nanoparticles (TWMNPs) was investigated. To prepare the TWMNPs, FeCl3.6H(2)O was dissolved in double distilled water (DDW) and 20 g of pulp tea was added slowly and stirred, after 30 min TWMNPs adsorbent were separated through an external magnetic field and washed three times with double distilled water (DDW) and ethanol then dried at 60 degrees C. The FESEM test of TWMNPs shows the particle size in the range of 15-20 nm and spherical/cuboid-shaped crystal structure of Fe3O4 (magnetite). X-ray analysis showed that the main XRD diffraction peaks of TWMNPs are related to Fe3O4, HighScore plus X'Pert software was used to identify the phase in this sample. The specific surface area of the prepared magnetite nanoparticles was 25.2 m(2).g(-1). The pore volume, maximum pore radius, and VSM of TWMNPs were 14.4 cm(3).g(-1), 2.3 nm, and 3.37-2.41, respectively. The effects of various parameters, such as contact time, pH, concentration, and adsorbent dosage, were studied. The experimental isotherm data were analyzed using the Langmuir and Freundlich models, and it was found that the removal process followed the Langmuir isotherm and the maximum adsorption capacity calculated by Langmuir fitting was 10.67 mg.g(-1). In addition, the adsorption kinetics followed the first-order kinetic model and the value of rate constant was found to be 14.04 x 10(-2) min(-1). The results showed that increasing the pH level led to a rise in the response level and Pb (II) removal. Also, the trend in Pb (II) removal and response level had an increase with increasing the initial concentration of Pb (II). Increasing contact time from 5 to 20 minutes has a slight effect on Pb (II) removal. Considering the results, TWMNPs could lead to suitable results for the removal of Pb (II) from wastewater containing this metal. And the maximum adsorption capacity was found to be 10.67 mg.g(-1).
Materials Chemistry and Physics (02540584) 307
The excess conductivity analysis is used to study the effects of Al2O3–15 wt% ZrO2 (AlZr) nanocomposite on the superconducting properties of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ (BiPb-2223) phase. A series of (BiPb-2223)1-x/(AlZr)x composite samples (0.0 wt% ≤ x ≤ 1 wt%) were synthesized by the conventional solid-state reaction method. The structural and morphological properties of the synthesized composites were studied using X-ray diffraction and scanning electron microscopy. Results showed that adding AlZr nanocomposite up to 0.5 wt% improves the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ phase formation. The excess conductivity analysis was carried out using Aslamazov–Larkin and Lawrence– Doniach approaches. The results indicated that the Fermi energy EF, Fermi velocity VF, and coherence length along the c axis ξc(0) decrease with increasing the AlZr nanocomposite concentration. The ξc(0) value decreases from 3.68 Å for AlZr free sample to 2.70 Å for x = 1.0 wt%. Moreover, superconducting critical parameters, including lower and upper critical magnetic fields (Bc1(0) and Bc2(0)) and critical current density (Jc(0)), were estimated by the Ginsberg-Landau theory. Obtained values indicated a remarkable enhancement in the mentioned critical parameters by adding the AlZr nanocomposite. The Jc(0) value enhances from 1.4 × 103 A/cm2 for AlZr free sample to 3.5 × 103 A/cm2 for the sample with 1.0 wt% additives, which shows that the Jc(0) is improved by about 150%. In addition, the critical magnetic fields are improved by about 80% in the sample containing 1.0 wt% AlZr compared to the AlZr-free sample. The observed improvement in the superconducting parameters is most likely attributed to the flux pinning capability and intergranular coupling enhancement. © 2023 Elsevier B.V.
Yavari, H. ,
Ghoshani m., ,
Mozaffari, M. ,
Acet M. ,
Hosseini, M. ,
Vashaee, D. Nanomaterials (20794991) 13(5)
In this study, we investigate the enhancement of exchange bias in core/shell/shell structures by synthesizing single inverted core/shell (Co-oxide/Co) and core/shell/shell (Co-oxide/Co/Co-oxide) nanostructures through a two-step reduction and oxidation method. We evaluate the magnetic properties of the structures and study the effect of shell thickness on the exchange bias by synthesizing various shell thicknesses of Co-oxide/Co/Co-oxide nanostructures. The extra exchange coupling formed at the shell-shell interface in the core/shell/shell structure leads to a remarkable increase in the coercivity and the strength of the exchange bias by three and four orders, respectively. The strongest exchange bias is achieved for the sample comprising the thinnest outer Co-oxide shell. Despite the general declining trend of the exchange bias with Co-oxide shell thickness, we also observe a nonmonotonic behavior in which the exchange bias oscillates slightly as the shell thickness increases. This phenomenon is ascribed to the dependence of the antiferromagnetic outer shell thickness variation at the expense of the simultaneous opposite variation in the ferromagnetic inner shell.
Physica B: Condensed Matter (09214526) 625
Zinc substituted spinel ferrite nanoparticles are appropriate for magnetic fluid hyperthermia. Stable suspensions of Zn2+ substituted magnetite (ZnxFe3-xO4, 0 ≤ x ≤ 0.20) nanoparticles in aqueous solutions (pH 5.5) were synthesized by means of co-precipitation approach, using citric acid (CA) and pluronic F127 as surfactants for hyperthermia application. The specimens were characterized by different methods. XRD patterns of the precipitates confirmed that all specimens have single phase cubic spinel structures and their lattice parameters increased as Zn2+ content increased. Mean crystallite sizes of the uncoated specimens were determined to be around 28 nm, using Scherrer's formula. By increasing the Zn2+ content, Curie temperature of the uncoated specimens reduced from 545 to 410 °C monotonically caused by reduction in super-exchange interactions. Room temperature saturation magnetizations of the uncoated specimens increased to 98.8 emu/g for x = 0.10 initially, and then decreased to 79.6 emu/g for x = 0.20. It is attributed to the replacement of paramagnetic Fe3+ ions by diamagnetic Zn2+ ones and spin canting. FTIR spectra reconfirmed formation of pure magnetite and Zn2+ substituted magnetite nanoparticles and also proved the presence of ligands on the surface of the nanoparticles. TEM investigation showed that mean particle sizes of the coated nanoparticles were in the range of 35–40 nm. The obtained ferrofluids showed a good stability in aqueous medium (pH 5.5) and according to the room temperature magnetic measurements, heating efficiency is scarcely released due to relaxation processes. Maximum obtained specific loss power (SLP) was 539 W/g and that of intrinsic loss power (ILP) was 7.26 nHm2/kg for x = 0.05 (f = 290 kHz, H = 16 kA/m) with a nanoparticle concentration as low as 1.2 mg/ml, which is a promising candidate for magnetic hyperthermia applications potentially. © 2021 Elsevier B.V.
Journal of Alloys and Compounds (09258388) 907
In high-temperature ceramic superconductors, vortices motion is induced by the strong thermal fluctuations because of the thermally activated flux flow (TAFF). The TAFF impedes the transport properties and critical current density of superconductors. It has been reported that adding nano-scale impurities can induce artificial pining centers that may improve inter-granular connections and flux pinning strength in ceramic superconductors. Here, the effects of different amounts (0.0–1.0 wt%) of ZnO nanoparticles on the TAFF behavior and zero temperature activation energy of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase have been studied using the modified TAFF model. Moreover, the impacts of the additive on the inter-granular traits and the Josephson coupling energy of the superconducting phase have been investigated using AC susceptibility measurements. Vortex phases analysis indicates that all composites show a vortex glass to vortex liquid phase transition at Tg. The vortex liquid phase is divided into the critical region existing in a finite temperature region just above Tg and the TAFF region present in the finite temperature region above it. It was found that the TAFF region is shifted to the higher temperatures and gets narrower, as the ZnO nanoparticles concentration enhances from 0.0 to 0.2 wt%. The vortex glass to vortex liquid transition temperature, Tg, increases from 93.8 K for the sample without additive to 101.0 K for the composite with 0.2 wt% ZnO nanoparticles. In addition, the zero-temperature activation energy (U0/KB) increases from ~0.4 × 105 K for the sample without additive to ~1.4 × 105 K for the composite with 0.2 wt% ZnO nanoparticles and then decreases for more ZnO concentrations. Moreover, it was found that the Josephson coupling energy Ej increases from ~0.039 eV for the sample without additive to ~0.136 eV for the composite with 0.2 wt% ZnO nanoparticles. These results point out a significant enhancement of the activation energy, flux pinning capability, and inter-granular coupling of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase with the addition of the 0.2 wt% ZnO nanoparticles. © 2022 Elsevier B.V.
Journal of Superconductivity and Novel Magnetism (15571947) 34(10)pp. 2471-2477
Two single-phase iron and cobalt ferrite nanoparticles and a bi-magnetic soft/hard nanostructure of Fe3O4/CoFe2O4 were synthesized through the coprecipitation method at 80 °C. Also, a sample is made just by mixing the two single-phase ferrite nanoparticles. Assessment through XRD indicates that spinel structure was formed in all samples. The mean crystallite sizes of the single phase ferrites were estimated by applying Williamson–Hall method on the XRD patterns, which are 9 and 16 for iron and cobalt ferrite nanoparticles, respectively. The TEM results confirmed the formation of the spherical core/shell nanostructure with narrow size distribution (47 nm). The study of the different magnetic properties (HC, MS, TB, and TC) indicates that the magnetic behavior of the exchange coupled core/shell nanostructure was significantly different from that of the physically mixed sample. This difference is a fingerprint to distinguish an exchange coupled core/shell nanostructure from a physical mixture. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Scientific Reports (20452322) 11(1)
The major limitations of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductor are weak flux pinning capability and weak inter-grains coupling that lead to a low critical current density and low critical magnetic field which impedes the suppleness of this material towards practical applications. The addition of nanoscales impurities can create artificial pining centers that may improve flux pinning capability and intergranular coupling. In this work, the influences of ZnO nanoparticles on the superconducting parameters and pseudogap properties of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductor are investigated using fluctuation induced conductivity analyses. Results demonstrate that the ZnO nanoparticles addition improves the formation of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ phase significantly. Various superconducting parameters include coherence length along c-axis (ξc(0)), penetration depth (λpd(0)), Fermi velocity (vF), Fermi energy (EF), lower and upper critical magnetic fields (Bc1(0) and Bc2(0) respectively) and critical current density (Jc(0)), are estimated for samples with different amounts of ZnO nanoparticles. It is found that the values of the Bc1(0), Bc2(0), and Jc(0) are improved significantly in the 0.2 wt% ZnO added sample in comparison to the ZnO-free sample. The magnitude and temperature dependence of the pseudogap Δ*(T) is calculated using the local pairs model. The obtained values of Tpair, the temperature at which local pairs are transformed from strongly coupled bosons into the fluctuating Cooper pairs, increases as the added ZnO nanoparticles concentration enhances up to 0.2 wt%. Also, the estimated values for the superconducting gap at T = 0 K (Δ(0)) are decreased from about 26 meV in ZnO-free sample to about 22 meV in 0.2 wt% ZnO added sample and then increases for higher values of additive. © 2021, The Author(s).
Scientific Reports (20452322) 11(1)
In this work, Sm3+ and Zn2+ co-substituted magnetite Zn0.1SmxFe2.9-xO4 (x = 0.0, 0.01, 0.02, 0.03, 0.04 and 0.05) nanoparticles, have been prepared via co-precipitation method and were electrostatically and sterically stabilized by citric acid and pluronic F127 coatings. The coated nanoparticles were well dispersed in an aqueous solution (pH 5.5). Magnetic and structural properties of the nanoparticles and their ferrofluids were studied by different methods. XRD studies illustrated that all as-prepared nanoparticles have a single phase spinel structure, with lattice constants affected by samarium cations substitution. The temperature dependence of the magnetization showed that Curie temperatures of the uncoated samples monotonically increased from 430 to 480 °C as Sm3+ content increased, due to increase in A-B super-exchange interactions. Room temperature magnetic measurements exhibited a decrease in saturation magnetization of the uncoated samples from 98.8 to 71.9 emu/g as the Sm3+ content increased, which is attributed to substitution of Sm3+ (1.5 µB) ions for Fe3+ (5 µB) ones in B sublattices. FTIR spectra confirmed that Sm3+ substituted Zn0.1SmxFe2.9-xO4 nanoparticles were coated with both citric acid and pluronic F127 properly. The mean particle size of the coated nanoparticles was 40 nm. Calorimetric measurements showed that the maximum SLP and ILP values obtained for Sm3+ substituted nanoparticles were 259 W/g and 3.49 nHm2/kg (1.08 mg/ml, measured at f = 290 kHz and H = 16kA/m), respectively, that are related to the sample with x = 0.01. Magnetic measurements revealed coercivity, which indicated that hysteresis loss may represent a substantial portion in heat generation. Our results show that these ferrofluids are potential candidates for magnetic hyperthermia applications. © 2021, The Author(s).
Ceramics International (02728842) 47(4)pp. 5133-5144
This study aimed to investigate the effect of milling time on the structural and exchange bias properties of two exchange-coupled nanocomposite systems that were prepared by mechanical milling. The first system consists of an antiferromagnet (CoO), named CoO-series and the second one consists of a mixture of a ferromagnet with an antiferromagnet (10 wt% Co + CoO), called MIX-series and both systems were milled for various times. Upon field cooling, going through low temperature (5 K), hysteresis loop shifts, coercivity enhancements, and saturation magnetization reductions were observed as milling time increases. Noticeable enhancements of exchange bias (270 Oe) and coercivity (1039 Oe) of the CoO-series after 10 h of milling, in comparison with those of unmilled ones (16 Oe) and (136 Oe) respectively, showed that the main structural changes occurred at the first milling hours. Introduction of large structural defects, the formation of cobalt and crystallite size reduction, ensuing from milling, can be the causes of an increase in exchange bias and coercivity. On the other hand, ferromagnet-antiferromagnet exchange coupling induces by milling is another origin for exchange bias. The results show that ferromagnet-antiferromagnet ratio and/or crystallite sizes play key roles in exchange bias enhancement. So that milled CoO-series with lower Co content in comparison with that of MIX-series and finer crystallites have considerable higher exchange bias. © 2020
Journal of Superconductivity and Novel Magnetism (15571947) 34(11)pp. 2933-2944
The cation and cation vacancy distributions in Zn2+ substituted maghemite (γ-Fe2 (1-x/3) ZnxO3, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles, which were synthesized directly via one pot room temperature co-precipitation method, were obtained by positron annihilation lifetime spectroscopy, coincidence Doppler broadening spectroscopy, and Rietveld refinement of XRD patterns. The analyses show that the substitution of small amounts of zinc ions for iron ones in maghemite (x ≤ 0.1) leads to an increase in the number of cation vacancies, while more substitutions cause to a decrease in cation vacancies. For the samples with x = 0.0 and 0.1, more of vacancies are placed at B sites, whereas for others they are placed at the A ones. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Physica B: Condensed Matter (09214526) 583
The Sendust alloy was prepared by mechanical alloying technique. The surface treatment process was carried out on the as-milled powders by hydrochloric acid, while irradiated by ultrasonic waves. EDS analysis indicated that surface-treated powders consisted of iron, silicon, aluminum, and oxygen elements. The FTIR spectrum of surface-treated powders had extra absorption bands related to aluminum oxides compared with as-milled powders. Results showed that although for cores made by surface-treated powders, both the real and imaginary parts of permeability decrease with respect to those for cores made by as-milled powders but significant reduction of imaginary part resulted in an increase in the quality factor remarkable. The cores were annealed in Ar atmosphere at temperatures 400, 500, and 600 °C for 1 h. The results show that the surface treatment process has led to a thermal stable coating layer on the Sendust powders up to 600 °C. © 2019 Elsevier B.V.
Ghoshani m., ,
Sánchez e.h., ,
Lee s.s., ,
Singh g., ,
Yaacoub n., ,
Peddis d., ,
Mozaffari, M. ,
Binns c., ,
De toro j.a., ,
Normile p.s., Nanotechnology (09574484) 32(6)
Exchange bias (EB) effects linked to surface spin freezing (SSF) are commonly found in iron oxide nanoparticles, while signatures of SSF in low-field temperature-dependent magnetization curves have been much less frequently reported. Here, we present magnetic properties of dense assemblies of similar-sized (∼8 nm diameter) particles synthesized by a magnetite (sample S1) and a maghemite (sample S2) method, and the influence of long-term (4 year) sample aging under ambient conditions on these properties. The size of the EB field of the different sample (fresh or aged) states is found to correlate with (a) whether a low-temperature hump feature signaling the SSF transition is detected in out-of-phase ac susceptibility or zero-field-cooled (ZFC) dc magnetization recorded at low field and with (b) the prominence of irreversibility between FC and ZFC curves recorded at high field. Sample S1 displays a lower magnetization than S2, and it is in S1 where the largest SSF effects are found. These effects are significantly weakened by aging but remain larger than the SSF effects in S2, where the influence of aging is considerably smaller. A non-saturating component due to spin disorder in S1 also weakens with aging, accompanied by, we infer, an increase in the superspin and the radius of the ordered nanoparticle cores. X-ray diffraction and Mössbauer spectroscopy provide indication of maghemite-like stoichiometry in both aged samples as well as thicker disordered particle shells in aged-S1 relative to aged-S2 (crystallographically-disordered and spin-disordered according to diffraction and Mössbauer, respectively). The pronounced diminution in SSF effects with aging in S1 is attributed to a (long-term) transition, caused by ambient oxidation, from magnetite-like to maghemite-like stoichiometry, and a concomitant softening of the spin-disordered shell anisotropy. We assess the impact of this anisotropy on the nature of the blocking of the nanoparticle superspins. © 2020 IOP Publishing Ltd.
Journal of Materials Science: Materials in Electronics (09574522) 31(3)pp. 1891-1903
In this work, Zn2+-substituted maghemite (γ-Fe2(1−x/3 ) ZnxO3, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles were synthesized via one-pot coprecipitation method at room temperature. Their structural and magnetic properties were studied by X-ray diffraction (XRD), magnetic thermogravimetry (TG/M/), vibrating sample magnetometry (VSM) and Fourier transform infrared (FTIR) spectroscopy methods. XRD analysis shows that all as-prepared samples have a spinel structure and their lattice constants change from 8.334 to 8.391 Å, depending on the Zn2+ content. Mean crystallite sizes of the as-prepared nanoparticles were estimated by Scherrer’s formula, which are between 3.4 and 4.9 nm. FTIR analysis reconfirms maghemite phase formation. Curie temperature of the samples was determined under two different conditions, one in uncapsulated form and another one in vacuumed quartz capsule, using TG/M/ method. The results show that the Curie temperature of the samples, measured in the uncapsulated form, is decreased from 515 to 330 °C as Zn2+ content increases. Also Curie temperature of the capsulated samples exhibits a reduction from 580 to 280 °C. Room-temperature magnetic measurements illustrate that as Zn2+ content increases, saturation magnetization initially increases from 53 emu/g to 54 emu/g for x = 0.1 and then decreases to 42 emu/g. These variations were discussed based on A and B sites occupations by diamagnetic and paramagnetic ions and reduction in A–A, B–B and A–B superexchange interactions, as a result of both increase in lattice constant and presence of more diamagnetic Zn2+ ions in the structure. These nanoparticles are suitable for fabrication of Faraday rotation devices potentially. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Journal of Superconductivity and Novel Magnetism (15571947) 31(8)pp. 2547-2552
In this study, Sendust alloy (Fe85Si9.6Al5.4) was fabricated by mechanical alloying process, and its crystal structure and magnetic properties were investigated. Sendust alloy has excellent soft magnetic properties and is widely used in different applications. Raw materials (Fe, Si, and Al) were milled by a planetary ball mill at different milling times, from 5 to 20 h. The resulted alloys were annealed at 1373 and 1473 K for 2 h, and the effect of annealing temperature was investigated on the magnetic properties. Crystal structure of the samples was investigated by X-ray diffractometery method. The results indicated that saturation magnetization of 10-h milled sample was at maximum, and it decreased both by increasing milling time and by annealing. These variations were discussed based on phase transformation from ordered to disordered phases and/or vice versa. The maximum saturation magnetization obtained, 156 emu/g, was comparable by those reported for Sendust alloy, which was prepared by other methods. Magnetization–temperature curves of the alloys and annealed ones were recorded by a Faraday balance. Two clear drops were observed on each M-T curve of the as-milled samples that displayed the existence of two different magnetic phases. On the other hand, there is just one drop on the M-T curves of the annealed samples, indicating that these samples were in a less disordered phase. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.
Hadadian, Y. ,
Sampaio, D.R. ,
Ramos, A.P. ,
Carneiro, A.A. ,
Mozaffari, M. ,
Cabrelli, L.C. ,
Pavan, T.Z. Journal of Magnetism and Magnetic Materials (03048853) 465pp. 33-43
Biomedical application of magnetic nanoparticles is a rapidly growing research field. For medical diagnostic purposes, these nanoparticles are mostly used as imaging contrast agents. Magneto-motive ultrasound (MMUS) is an example of imaging techniques where superparamagnetic nanoparticles are used as contrast agent. Since it is a relatively new technique, much research is yet in progress to optimize the magnetic properties of these contrast agents. In this study, Zn-substituted magnetic (nominal composition ZnxFe1−xFe2O4, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles with aim of enhancing the saturation magnetization were successfully synthesized by the coprecipitation method. The effect of zinc on morphology, structure and magnetic properties of the prepared nanoparticles was studied and their potential for MMUS imaging was investigated. X-Ray diffraction results showed that all samples had spinel structure and incorporating zinc in magnetite structure led to an increase in its lattice parameter, on the other hand TEM images revealed that particle size was decreased with zinc concentration. EDX analysis of the samples confirmed the incorporation of zinc in magnetite structure with a relatively good agreement with nominal values. Low, room and high temperature magnetic properties of the samples were investigated using vibrating sample magnetometer (VSM). Room temperature M-H curves along with zero-field-cooling measurements showed all samples were superparamagnetic and saturation magnetization at x = 0.1 zinc concentration increased drastically. All prepared samples were examined as contrast agents in MMUS imaging and the results confirmed the direct role of magnetization in enhancement of MMUS signals. © 2018 Elsevier B.V.
Gheiratmand t., ,
Madaah hosseini h.r., ,
Shalbaf f., ,
Mohhebali m., ,
Mozaffari, M. ,
Arabi s.h., ,
Farzanegan f., Journal of Superconductivity and Novel Magnetism (15571947) 30(11)pp. 3085-3090
Iron-borosilicate magnetic composites could be applied as a soft magnetic material in high temperature and high frequency applications. In this research, the magnetic properties of soft magnetic composites with different iron particle sizes made by spark plasma sintering have been investigated. Different magnetic properties such as permeability, loss factor, and quality factor were examined up to frequencies in the order of kilohertz. The microstructural observations indicated the distribution of borosilicate on the iron grain boundaries. The results revealed that the loss factor is smaller for composites with fine particles at high frequencies. In addition, the magnetic impedance for smaller particles was greater. It was also found that the permeability and quality factor of composites with coarse particles are larger than those of fine particles. Indeed, when the particles become coarse, the density of porosities and consequently, the demagnetizing fields decrease which result in the increase of permeability. Furthermore, when the size of particles reduces, the density of grain boundaries enhances which is the main reason of lower loss factor achieved in the composites with fine particles. © 2017, Springer Science+Business Media New York.
Applied Radiation and Isotopes (09698043) 125pp. 18-22
In this work we investigated vacancies in maghemite and Zn substituted maghemite (γ-Fe2−yZn3y/2O3, y=0.0, 0.11, 0.24, 0.36, 0.50 and 0.66) nanoparticles using coincidence Doppler broadening and positron annihilation lifetime spectroscopy. Coincidence Doppler broadening spectroscopy (CDBS) measurements showed that the positrons annihilated in cation vacancies that surrounded by oxygen anions. Also, the CDBS showed that in pure maghemite and in the y=0.11 samples the vacancies are in octahedral and tetrahedral sites, respectively. For other samples they are distributed in both octahedral and tetrahedral sites. The positron annihilation lifetime spectroscopy (PALS) measurements confirmed the results of the CDBS measurements and also exhibited that the number of vacancies in y=0.36 sample is less than the other samples. This is attributed to Zn substituted magnetite phase in this sample as well as Zn substituted maghemite phase. © 2017 Elsevier Ltd
Journal of Magnetics (12261750) 22(2)pp. 169-174
In this work, lithium ferrite (Li0.5Fe2.5O4) nanoparticles were prepared via mechanochemical processing and subsequent heat treatment at a relatively low (600 °C) calcining temperature. The raw materials used were high purity Fe2O3 and Li2CO3 that were milled for between 2 and 20 h. The milled powders were then calcined at temperatures of 500 and 600 °C for 5 h in air. XRD results show that optimum conditions to obtain single phase lithium ferrite nanoparticles with a mean crystallite size of about 23 nm, using Scherrer’s formula, are 10 h milling and calcination at 600 °C. Saturation magnetization and coercivity of the single phase Li ferrite nanoparticles are 44.6 emu/g and 100 Oe respectively, which are both smaller than those of the bulk Li ferrite. The Curie temperature of the single sample was determined by a Faraday balance, which is 578 °C and smaller than that of bulk Li ferrite. © 2017 Journal of Magnetics and The Korean Magnetics Society. All rights reserved.
Journal of the Chinese Chemical Society (00094536) 63(10)pp. 886-892
An organic light-emitting diode was fabricated using cadmium selenide (CdSe)/poly(N-vinylcarbazole) nanocomposite as the hole transport layer (HTL). The CdSe nanoparticles (NPs) with a mean crystallite size of 6.2 nm were prepared by high-energy ball milling. Based on the current–voltage curves, the threshold voltage (V th) of the composite diode was found to be ~1.3 ± 0.1 V lower than that of the diode without CdSe, with a significant increase in the current density for the composite diode. Moreover, the electroluminescence (EL) properties (luminous flux, emittance, and intensity) of the diode were found to be enhanced by ~16% with respect to those of the diode without CdSe. The decrease of the threshold voltage and the increase of the current density and the EL were due to the CdSe NPs that operate as hole trap centers in the HTL. © 2016 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Hasanpour, A. ,
Mozaffari, M. ,
Shahrokhvand s.m., ,
Mozaffari, M. ,
Hasan rozatian, A.S. ,
Hamidi s.m., ,
Tehranchi m.m., APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING (09478396) 122(1)pp. 1-5
In this work, cerium-substituted yttrium iron garnet (CexY3-xFe5O12, x = 0.25-1) targets were fabricated by conventional ceramic method at different temperatures, and their crystal structures were investigated by X-ray diffraction method. The results showed that the minimum calcining temperature required to get single-phase targets depends on x value and decreased by increasing x value. Then, thin films of the targets were deposited on GGG (444) single-crystal substrates by pulsed laser deposition technique. Based on the previous studies, preferred (444) oriented CexY3-xFe5O12 thin films were fabricated under optimum conditions. Faraday rotation of the thin films was measured at 635 nm wavelength, and the results showed that Faraday rotation and sensitivity constant increased by increasing x value. Scanning electron microscope images showed that by increasing x value, cracks on the thin films' surface increased. Atomic force microscopy images showed that the films have smooth surfaces and the surface roughness decreased by increasing the x value.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (0168583X) 375pp. 71-78
Single phase copper substituted nickel ferrite [removed]Ni1-xCuxFe2O4[removed] (x = 0.0, 0.1, 0.3 and 0.5) nanoparticles were synthesized by the sol-gel method. TEM images of the samples confirm formation of nano-sized particles. The Rietveld refinement of the X-ray diffraction patterns showed that lattice constant increase with increase in copper content from 8.331 for x = 0.0 to 8.355 [removed]Å[removed] in x = 0.5. Cation distribution of samples has been determined by the occupancy factor, using Rietveld refinement. The positron lifetime spectra of the samples were convoluted into three lifetime components. The shortest lifetime is due to the positrons that do not get trapped by the vacancy defects. The second lifetime is ascribed to annihilation of positrons in tetrahedral (A) and octahedral (B) sites in spinel structure. It is seen that for x = 0.1 and 0.3 samples, positron trapped within vacancies in A sites, but for x = 0.0 and 0.5, the positrons trapped and annihilated within occupied B sites. The longest lifetime component attributed to annihilation of positrons in the free volume between nanoparticles. The obtained results from coincidence Doppler broadening spectroscopy (CDBS) confirmed the results of positron annihilation lifetime spectroscopy (PALS) and also showed that the vacancy clusters concentration for x = 0.3 is more than those in other samples. Average defect density in the samples, determined from mean lifetime of annihilated positrons reflects that the vacancy concentration for x = 0.3 is maximum. The magnetic measurements showed that the saturation magnetization for x = 0.3 is maximum that can be explained by Néel's theory. The coercivity in nanoparticles increased with increase in copper content. This increase is ascribed to the change in anisotropy constant because of increase of the average defect density due to the substitution of [removed]Cu2+[removed] cations and magnetocrystalline anisotropy of [removed]Cu2+[removed] cations. Curie temperature of the samples reduces with increase in copper content which can be explained based on Néel's theory. © 2016 Elsevier B.V. All rights reserved.
Journal of Superconductivity and Novel Magnetism (15571947) 28(10)pp. 3157-3162
One-step mechanochemical processing is one of the most useful and effective methods to produce nanoparticles. Prepared materials by this method show novel properties. In this work, Mg-substituted Zn ferrite (MgxZn1−xFe2O4; x = 0.0, 0.2, 0.4, 0.6) nanoparticles were prepared by one-step mechanochemical processing for the first time. In addition, bulk samples with the same compositions were prepared by conventional ceramic method, which served as reference samples. The samples were characterized by the X-ray diffraction and field emission electron microscopy. By a comparison between I(220)/I(222) intensity ratios in X-ray diffraction patterns of the samples prepared by one-step mechanochemical processing and those of the bulk samples, changes in the cation distribution of the samples prepared by one-step mechanochemical processing were followed. Lattice parameters and magnetic properties of the all samples were measured, and their behaviors were discussed. © 2015, Springer Science+Business Media New York.
Journal of Superconductivity and Novel Magnetism (15571947) 28(8)pp. 2337-2343
In this work, the effect of alumina (α-Al2O3) nanoparticle addition on the phase formation and superconducting properties of Bi1.6Pb0.4Sr2Ca2Cu3O10−y ((Bi,Pb)- 2223) system has been investigated. Six samples with different alumina nanoparticle contents (0.0, 0.1, 0.2, 0.3, 0.5, and 1 wt % of the sample’s total mass) were prepared by conventional solid-state reaction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods have been used to study phase formation and microstructure of the prepared samples, respectively. Also, electrical resistivity and critical current density of the prepared samples were measured by four-probe technique. AC susceptibility of the samples has been measured by an LCR meter. XRD results showed that addition of small amounts of the alumina nanoparticles improves (Bi,Pb)-2223 phase formation significantly. Temperature dependency of AC susceptibility measurements revealed that addition of α- Al2O3 nanoparticles improves the intergranular coupling. The I-V measurements show that critical current density of samples increased from about 36 A/cm2 for the alumina nanoparticle-free sample to about 107 A/cm2 for the sample with 0.5 wt % α-Al2O3 nanoparticles. © Springer Science+Business Media New York 2015.
Mozaffari, M. ,
Shatooti s., S. ,
Jafarzadeh, M. ,
Niyaifar m., ,
Aftabi, A. ,
Mohammadpour h., ,
Amiri, S. Journal of Magnetism and Magnetic Materials (03048853) 382pp. 366-375
Maghemite and Zn2+ substituted maghemite (γ-Fe2-y Zn3y/2O3, y=0.0, 0.11, 0.24, 0.36, 0.50 and 0.66) nanoparticles were prepared by coprecipitation method. The effect of Zn2+ substitution on the structural, morphological and magnetic properties of the nanoparitcles were studied by different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), magnetometry, magnetic thermogravimetry and Mössbauer spectroscopy. The results of XRD showed that all samples have spinel structure with an increase in lattice parameter by increasing the content of Zn2+. FTIR spectra were proved the synthesis of maghemite and Zn2+ substituted maghemite with appearance of the related absorption bands and band shift upon Zn2+ substitution. Morphological studies by FESEM demonstrated that the nanoparticles were uniform and spherical with average particle size in range of 20-24 nm. Room temperature magnetic measurements showed that as Zn2+ content increases, saturation magnetization initially increase up to 75.34 emu/g for y=0.11 and then decrease to 3.65 emu/g for y=0.66, due to substitution of magnetic Fe3+ by non-magnetic Zn2+. Decrease in Curie temperature of the samples, from 510 for maghemite to 250 °C for y=0.36, by increasing the Zn2+ substitution was a result of reduction of superexchange interactions between different sites. Then, the Curie temperature increased up to 680 °C for y=0.66 which was due to migration of some Zn2+ ions from A to B sites in the structure of spinel. Room temperature Mössbauer spectra exhibited that the sample with y=0.0 was superparamagnetic, while by increasing the content of Zn2+, relaxation effect increased by weakening of A-B exchange interaction. © 2015 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 379pp. 208-212
Superparamagnetic Y-substituted magnetite (YxFe3-xO4,with x = 0.00, 0.10, 0.15, 0.20 and 0.40) nanoparticles were synthesized via hydrothermal reduction route in the presence of citric acid. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM) and gradient field thermomagnetic measurement. The results showed that a minimum amount of citric acid is required to obtain single phase Y-substituted magnetite nanoparticles. Citric acid acts as a modulator and reducing agent in the formation of spinel structure and controls nanoparticle size and crystallinity. Mean crystallite sizes of the single-phase powders were estimated by Williamson- Hall method. Curie temperature measurement of the samples shows that as yttrium content increases, the Curie temperature decreases. Magnetic measurements show that the saturation magnetization of the samples decreases as x increases up to 0.15 and then increases to x = 0.20 and finally decreases again for x = 0.40. © 2014 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 350pp. 19-22
In this study Ni substituted cobalt ferrite nanoparticles (Ni xCo1-xFe2O4 where x=0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by the sol-gel method. Phase identification of the samples was performed by the X-ray diffraction (XRD) method and the mean crystallite sizes of the samples were obtained using Scherrer's formula. The results show that a minimum calcining temperature of 500 C is required to obtain single phase spinel structures for all the samples. It was observed that the lattice parameter of the samples decreases from 8.350 to 8.300 Å with increasing Ni content. Morphology of the samples was investigated by a field emission scanning electron microscope (FESEM). Also mean particle sizes of the samples were obtained from FESEM images and there no relation between particle size and Ni content was found. Magnetic measurements were carried out on the cold pressed samples and the results show that saturation magnetization decreases as x increases. Curie temperatures of the samples were determined and the results show that by increasing x values their Curie temperatures increase. This increase was explained based on the change in superexchange interactions between magnetic ions by substitution of Ni ions in Co ferrite. Also the coercive forces of the samples decreased with increasing x values which was explained by the changes in magnetocrystalline anisotropy. © 2013 Elsevier B.V.
Journal of Magnetism and Magnetic Materials (03048853) 354pp. 119-124
In this work cobalt-substituted magnetite (CoxFe 1-xFe2O4, x=0, 0.25, 0.50 and 0.75) nanoparticles were synthesized by coprecipitation method and their structural and magnetic properties were investigated. X-ray diffraction was carried out and the results show that all of the samples have single phase spinel structure. Microstructure of the samples was studied using a field emission scanning electron microscope and the results show that particle sizes of the prepared nanoparticles were uniform and in the 50-55 nm range. Room temperature magnetic properties of the nanoparticles were measured by an alternating gradient force magnetometer and the results revealed that substituting cobalt for iron in magnetite structure, changes the magnetite from a soft magnetic material to a hard one. So that coercivity changes from 0 (a superparamagnetic state) to 337 Oe (a hard magnetic material), which is a remarkable change. Curie temperatures of the samples were determined by recording their susceptibility-temperature (χ-T) curves and the results show that by increasing cobalt content, Curie temperature of the samples also increases. Also χ-T curves of the samples were recorded from above Curie temperature to room temperature (first cooling), while the curves in the second heating and second cooling have the same behaviour as the first cooling curve. The results depict that all samples have different behaviour in the first cooling and in the first heating processes. This shows remarkable changes of the cation distribution in the course of first heating. © 2013 Elsevier B.V.
Journal of Superconductivity and Novel Magnetism (15571947) 27(11)pp. 2563-2567
In this work, single phase zinc ferrite (ZnFe2O4) nanoparticles with a mean crystallite size of 12 nm were successfully prepared just by high energy wet milling of metallic Zn and Fe powders and water as the raw materials, without any subsequent heat treatments. Variation of the magnetization with respect to temperature was studied by Faraday balance. Room temperature M–H curve of the as-milled powder has an s-shape, which shows it has ferrimagnetic order. To investigate the effect of annealing on magnetic properties of the as-milled powder, it was annealed at different temperatures from 150 to 800 °C and characterized by XRD and magnetometry. The results show that cation distribution of the as-milled nanoparticles is different from that of the bulk zinc ferrite (normal spinel) and by annealing it changes drastically, and finally, it changes to that of the bulk one. © 2014, Springer Science+Business Media New York.
Beiranvand a., ,
Hamidi s.m., ,
Abooalizadeh z., ,
Mozaffari, M. ,
Amighian j., J. ,
Tehranchi m.m., ,
Yousif a., Life Science Journal (discontinued) (10978135) 10(SUPPL.2)pp. 181-184
Thin magnetic films have been prepared by pulsed-laser deposition from targets of the orthoferrites: Y1- xBixFeO= (x=0, 0.1, 0.15 and 0.2). The targets created by sol-gel method and characterized via X-ray diffraction, Scanning electron microscope. All layers were deposited onto quartz substrates in a vacuum chamber evacuated down to 4×10-5 mbar and the oxygen ambient gas pressure was 150mbar. After deposition, films were recrystallized with annealing procedure at 600 °C for 40 minutes. The magnetic behavior of the thin films was investigated using Faraday rotation measurement setup under a DC magnetic field. The results show that Faraday rotation angle increases as Bi content increases.
Journal of Superconductivity and Novel Magnetism (15571947) 26(3)pp. 675-678
MnFe2O4 nanoparticles were synthesized by low-power ultrasonic assisted co-precipitation at two different aging times. In order to investigate the effect of ultrasonic waves on phase formation and magnetic properties of Mn ferrite nanoparticles, two other samples were synthesized in the same conditions but in the absence of ultrasonic waves. Structural and morphological properties of the nanoparticles were examined by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The presence of ultrasonic waves through the reaction medium led to form a single phase of MnFe2O4 at 15 min aging time, while this time was insufficient to form a single phase in the absence of ultrasonic waves. At 60 min aging time, the crystallinity of the sample synthesized in the presence of ultrasonic waves was greater and its particle size was bigger than those of the sample synthesized in the absence of ultrasonic waves. The observed results were evaluated from physico-chemical point of view. It was concluded that the ultrasonic waves led to a slower nucleation rate. The magnetic properties of the nanoparticles were examined by permeameter and Faraday-balance equipment. The saturation magnetization of the sample prepared in the presence of ultrasonic waves was enhanced and its Curie temperature was reduced. © 2012 Springer Science+Business Media New York.
Gheisari m., M. ,
Mozaffari, M. ,
Niyaifar m., ,
Amighian j., J. ,
Soleimani r., Journal of Superconductivity and Novel Magnetism (15571947) 26(2)pp. 237-242
Wüstite nanoparticles have been prepared by mechanochemical processing (MCP), using high-purity hematite (α-Fe2O3) and iron (Fe) powders as the raw materials. In order to get a single-phase wüstite, different mole ratios of (Fe/Fe2O3) were milled. X-ray diffraction studies of the as-milled powders show that a single-phase wüstite was formed. Using the formula a=4.334-0.478x, for Fe1-x O, where "a" is the lattice parameter of wüstite, a nonstoichiometric composition of Fe0.93O was estimated for the wüstite single phase. A mean crystallite size of 13±1 nm was calculated for the single phase wüstite, using Scherrer's formula. The morphology of the powders was also checked by TEM. The room-temperature Mössbauer spectra of the samples supported the presence of Fe3+ in octahedral sites of wüstite phase, which is a sign of its nonstoichiometry. Hysteresis loops of the as-milled powders at 5 K and room temperature have been obtained by SQUID and by VSM systems, respectively. The loops show nonzero coercivity, in contrast to the bulk wüstite. The observed magnetizations can be explained by a model based on the spinel-type defect clusters in nonstoichiometry wüstite. Room temperature magnetic measurements showed that nanosized prepared wüstite ferrimagnetic-like behavior was interpreted according to spinel-like defect clusters. Therefore, small exchange bias effects 20 Oe and 38 Oe were observed in the magnetization curves at room and 5 K temperatures, respectively. According to the Dimitrov model, in the Fe0.93O nonstoichiometry structure, there are 0.712 molecules of FeO and 0.072 molecules of Fe3O4, which the interaction between the antiferromagnetic (FeO) and ferrimagnetic (Fe 3O4) phases in the Fe1-x O can be the cause of the observed exchange bias effect in the hysteresis loops. © 2012 Springer Science+Business Media New York.
Avicenna Journal Of Medical Biotechnology (20084625) 5(2)pp. 96-103
Background: Magnetic nanoparticles in a variable magnetic field are able to produce heat. This heat (42-45°C) has more selective effect on fast dividing cancer cells than normal tissues. Methods: In this work magnetite nanoparticles have been prepared via coprecipitation and phase identification was performed by powder x-ray diffraction (XRD). Magnetic parameters of the prepared nanoparticles were measured by a Vibrating Sample Magnetometer (VSM). A sensitive thermometer has been used to measure the increase of temperature in the presence of an alternating magnetic field. To evaluate the cytotoxicity of nanoparticles, the suspended magnetite nanoparticles in liquid paraffin, doxorubicin and a mixture of both were added to the MDA-MB-468 cells in separate 15 ml tubes and left either in the RT or in the magnetic field for 30 min. Cell survival was measured by trypan blue exclusion assay and flow cytometer. Particle size distribution of the nanoparticles was homogeneous with a mean particles size of 10 nm. A 15°C temperature increase was achieved in presence of an AC magnetic field after 15 min irradiation. Results: Biological results showed that magnetite nanoparticles alone were not cytotoxic at RT, while in the alternative magnetic filed more than 50% of cells were dead. Doxorubicin alone was not cytotoxic during 30 min, but in combination with magnetite more than 80% of the cells were killed. Conclusion: It could be concluded that doxorubicin and magnetite nanoparticles in an AC magnetic field had combinatory effects against cells. © 2013, Avicenna Journal of Medical Biotechnology. All rights reserved.
Beiranvand a., ,
Mehdipour m., ,
Amighian j., J. ,
Yousif a., ,
Mozaffari, M. Life Science Journal (discontinued) (10978135) 10(SUPPL. 5)pp. 155-161
Nanopowders of Y1-xBixFeO3 (x=0.0, 0.1, 0.15 and 0.2) have been synthesized by the sol gel method. Xray diffraction identifications show that all the samples have orthorhombic structure and mean crystallite sizes of the nanopowders are in the range of 40 nm, using Scherrer's formula. Mean particle sizes of the samples were obtained by TEM, which is in the range of 75 nm. The 57Fe Mössbauer spectra of Y1-xBixFeO3 nanopowders at 78 and 295 K have been recorded and the results show that all the Fe3+ ions are almost at the symmetrical positions. Room temperature magnetization measurements show that with increasing Bi content up to 0.15, the magnetization increases, whereas it decreases for the sample with x=0.2. M-T curves of the samples were recorded at applied fields of 40 and 13500 Oe. Although all samples show a metamagnetic behavior around Tk=225 °C and at higher applied field, but for the sample with x=0.2, the behavior is more clear.
Journal of Magnetism and Magnetic Materials (03048853) 332pp. 157-162
In this work single phase Mn substituted magnetite (MnxFe 3-xO4, x=0-0.75) nanoparticles were prepared by the coprecipitation method. X-ray diffraction analysis showed that the prepared nanoparticles have a single-phase spinel structure. An average crystallite size of about 20 nm has been obtained for all the samples, using Scherrer's formula. Field emission scanning electron microscope images of the samples showed that the average particle sizes were about 25 nm. The Curie temperature (T C) of the samples were measured by a Faraday balance and decreased from 610 °C to 510 °C by increasing Mn content from x=0 to x=0.75. The M-H curves of the nanoparticles exhibited superparamagnetic behavior for all the samples except for x=0 and saturation magnetization (σs) decreased with increasing of Mn content. The temperature dependence of AC-susceptibility of samples at different frequencies reveals maxima corresponding to the different blocking temperatures. It was shown that the frequency dependence of the blocking temperature can be described by the Vogel-Fulcher law for superparamagnets, well. © 2012 Elsevier B.V.
Shahrokhvand s.m., ,
Hasan rozatian, A.S. ,
Mozaffari, M. ,
Hamidi s.m., ,
Tehranchi m.m., Journal of Physics D: Applied Physics (00223727) 45(23)
Cerium-substituted yttrium iron garnet (Ce xY 3xFe 5O 12 or Ce:YIG) thin films with a high Ce content are very hard to achieve because of the solubility limit of Ce in the yttrium iron garnet (YIG) structure. In this work a Ce:YIG target with nominal formula of CeY 2Fe 5O 12 was fabricated by the conventional ceramic method. Phase formation and crystal structure of the samples were investigated by the x-ray diffraction (XRD) method and the results showed that the minimum temperature to get a single phase CeY 2Fe 5O 12 is 1400°C. CeY 2Fe 5O 12 thin film was deposited on a GGG (444) single crystal substrate, using the pulsed laser deposition method and its microstructure and magneto-optical (MO) properties were studied. Trying different conditions, a preferred (444) oriented CeY 2Fe 5O 12 thin film was fabricated under an optimum condition. The results showed that a crystalline CeY 2Fe 5O 12/GGG thin film can be obtained by annealing of the as-deposited film at 600°C. XRD measurements on the annealed thin film showed that the mean grain size was 38nm, using Scherrer's formula. Scanning electron microscopy image of the annealed thin film showed that the mean grain size was 35nm, which is in good agreement with XRD measurements. Atomic force microscopy (AFM) image of the annealed sample showed that the thin film had a smooth surface. Faraday rotation provided by the thin film at wavelength =635nm was measured to be 2.4°νm 1 in a magnetic field of 600mT. Transmission spectrum of the thin film was recorded in the visible and near-infrared regions, from 400 to 1000nm, and it showed good transparency, more than 78%, in the near-infrared region. These measurements resulted in an MO figure of merit of 0.146, which is one of the highest values reported up to now. It is expected that CeY 2Fe 5O 12 thin films could be used as new Faraday rotator materials, applicable in optical isolators and circulators. © 2012 IOP Publishing Ltd.
Russian Journal of Physical Chemistry A (00360244) 86(2)pp. 264-267
In this work Bi-Fe 3O 4 nanocomposite was synthesized by room temperature milling of Bi 2O 3 and Fe powders using a planetary ball mill in air. The synthesis reaction proceeds with increase in milling time and is finished by about 4 h. The XRD pattern of the as-milled powder shows that the main phases are Bi and Fe 3O 4 without any extra phases. The average crystallite sizes of the constituents have been determined by Scherrers formula and they were 22 and 18 nm for Bi and Fe 3O 4 respectively. This was also confirmed by Transmission Electron Microscopy (TEM). Magnetic hysteresis loops at room temperature were recorded using a vibrating sample magnetometer (VSM). A tow-probe method was used to measure resistivity variation of the nanocomposite as a function of magnetic filed and temperature. We have observed a room temperature magnetoresistance (ρ 0 - ρ H )/ρ 0 as large as 17% in a magnetic field of 1 T. © 2012 Pleiades Publishing, Ltd.
Journal of Magnetism and Magnetic Materials (03048853) 324(14)pp. 2211-2217
Superparamagnetic and monodispersed aqueous ferrofluids of Zn substituted magnetite nanoparticles (Zn xFe 3-xO 4, x=0, 0.25, 0.3, 0.37 and 0.4) were synthesized via hydrothermal-reduction route in the presence of citric acid, which is a facile, low energy and environmental friendly method. The synthesized nanoparticles were characterized by X ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM) and the dynamic light scattering (DLS) method. The results showed that a certain amount of citric acid was required to obtain single phase Zn substituted magnetite nanoparticles. Citric acid acted as a modulator and reducing agent in the formation of spinel structure and controlled nanoparticle size and crystallinity. Mean particle sizes of the prepared nanoparticles were around 10 nm. The results that are obtained from XRD, magnetic and power loss measurements showed that the crystallinity, saturation magnetization (M S) and loss power of the synthesized ferrofluids were all influenced by the substitution of Zn in the structure of magnetite. The Zn substituted magnetite nanoparticles obtained by this route showed a good stability in aqueous medium (pH 7) and hydrodynamic sizes below 100 nm and polydispersity indexes below 0.2. The calculated intrinsic loss power (ILP) for the sample x=0.3 (e.g. 2.36 nH m 2/kg) was comparable to ILP of commercial ferrofluids with similar hydrodynamic sizes. © 2012 Elsevier B.V. All rights reserved.
Journal of Solid State Chemistry (1095726X) 187pp. 20-26
Monodispersed aqueous ferrofluids of iron oxide nanoparticle were synthesized by hydrothermal-reduction route. They were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and dynamic light scattering. The results showed that certain concentrations of citric acid (CA) are required to obtain only magnetic iron oxides with mean particle sizes around 8 nm. CA acts as a modulator and reducing agent in iron oxide formation which controls nanoparticle size. The XRD, magnetic and heating measurements showed that the temperature and time of hydrothermal reaction can affect the magnetic properties of obtained ferrofluids. The synthesized ferrofluids were stable at pH 7. Their mean hydrodynamic size was around 80 nm with polydispersity index (PDI) of 0.158. The calculated intrinsic loss power (ILP) was 9.4 nHm 2/kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia. © 2012 Elsevier Inc. All rights reserved.
Shaygan, M. ,
Nourbakhsh, A.A. ,
Mozaffari, M. ,
Shahshahan, M. ,
Nourbakhsh, M. Molecular Crystals and Liquid Crystals (15421406) 555pp. 94-103
The chromium and aluminium quantitiesrequired to synthesize nano-sized SrCr x Fe 12-xO 19 and SrAl xFe 12-xO 19 by the auto combustion route were optimized. XRD analysis showed that the optimum amounts were differed in two cases. A combination of 0.75 wt% of nano-sized SrFe 12O 19 and 0.75 wt% of the commercial additive, in chromium doped sample from solid state process(Cr 2O 3 addition), resulted in superior magnetic properties with increased intrinsic coercivity, remanence magnetization and rectangularity ratio. © 2012 Copyright Taylor and Francis Group, LLC.
Advanced Structured Materials (18698441) 5pp. 281-305
To date, nano-magnetic materials have gain great attention by the research community due to their importance for future applications. A brief introduction of Fe-FeO nanocomposites in the form of particles and thin films is given in the first part of this chapter. This includes definition, magnetic properties, preparation, structure and applications. Different preparation methods of Fe-FeO are then introduced in the second part of the chapter. These include mechanical alloying, high energy ball milling, mechanochemical processing, DC magnetron sputtering, molecular-beam-epitaxy, plasma gas condensation. Among these preparation techniques, mechanochemical processing has been fully explained. Different techniques and instruments which have been used to characterize the samples have been explained. These include XRD, TEM, VSM, Superconducting Quantum Interferences Devices (SQUID), and Mössbauer. Magnetic properties of the nanocomposites especially Fe-FeO have been presented in the final part of the chapter. These include magnetization, coercivity, Mössbauer, hysteresis loops, exchange bias effect, vertical shift, spin glass phase, rotational hysteresis, FC and ZFC hysteresis loops. © Springer-Verlag Berlin Heidelberg 2010.
Journal of Magnetism and Magnetic Materials (03048853) 323(23)pp. 2997-3000
NiFe2-xAlxO4 nanopowders, where x is from 0 to 1.5 with a step of 0.5, have been synthesized by the solgel method and the effect of non-magnetic aluminum content on their structural and magnetic properties were investigated. The X-ray diffraction (XRD) patterns revealed that the synthesized nanopowders are single phase with a spinel structure. Mean crystallite sizes of the samples were calculated by Scherrers formula and were in the range 2031 nm. The morphology of the nanopowders was investigated by TEM and the mean particle sizes of the samples were in the range 5580 nm. Magnetic hysteresis loops were recorded at room temperature in a maximum applied field of 3000 Oe. The results show that by increasing the aluminum content, the magnetizations of the nanopowders are decreased. This reduction is caused by non-magnetic Al3 ions, which by their substitutions the super exchange interactions between different sites will be reduced. It is also seen that the magnetizations of the nanopowders are lower than those related to their bulk counterparts. This reduction was found to be as a consequence of surface spin disorder. MT curves of the samples were obtained using a Faraday balance and by which the Curie temperatures of the powders were determined. The results that are obtained show that the Curie temperatures of the nanopowders are higher than those of their bulk counterparts. © 2011 Elsevier B.V. All rights reserved.
IFMBE Proceedings (16800737) 37pp. 1110-1112
In this work, Mn ferrite nanopowders were prepared by ultrasonic assisted co-precipitation method and were characterized. Phase identification of the nanopowders was performed by X-ray diffraction method and the mean crystallite size of the nanopowders was calculated by Scherrer's formula with necessary corrections. Magnetic parameters of the prepared nanopowders were measured by a vibrating sample magnetometer. A sensitive thermometer was used to measure the increase in temperature due to application of an alternating magnetic field on suspended magnetic nanopowders in water. Transmission electron microscope investigations showed that the particle size distribution was homogeneous and their mean particle size was in a good agreement with those obtained by Scherrer's formula. The results show that a single phase Mn ferrite can be obtained by ultrasonic assisted co-precipitation method at 70 °C with a mean particle size of 5 nm and a 5 °C increase was achievable in an AC magnetic field. © 2011 Springer-Verlag Berlin Heidelberg.
Iranian Journal of Environmental Health Science and Engineering (17352746) 8(3)pp. 189-200
In this study the efficiency of magnetic nanoparticles for removal of trivalent arsenic from synthetic industrial wastewater was evaluated. The nanoparticles was prepared by sol-gel method and characterized by X-ray methods including XRD, XRF, and SEM, and vibrating sample magnetometer (VSM). The results showed that synthesized nanoparticles were in the size range of 40-300 nm, purity of about 90%, and magnetization of nanoparticles was 36.5emu/g. In initial conditions including: pH=7, As(III) concentration of 10 mg/L, nanomagnetite concentration of 1g/L, shaking speed of 250 rpm and 20 minute retention time, 82% of As (III) was removed. Competition from common coexisting ions such as Na+, Ni2+, Cu2+, SO42-, and Cl- was ignorable but for NO3- was significant. The adsorption data of magnetite nanoparticles fit well with Freundlich isotherm equations. The adsorption capacity of the Fe3O4 for As (III) at pH=7 was obtained as 23.8 mg/g. It was concluded that magnetite nanoparticles have considerable potential in removal of As(III) from synthetic industrial wastewaters.
Tehranchi m.m., ,
Hamidi s.m., ,
Hasanpour, A. ,
Mozaffari, M. ,
Amighian j., J. Optics and Laser Technology (00303992) 43(3)pp. 609-612
The effect of target rotation rate on the structural and morphological properties of pulsed laser deposition grown Bi:YIG garnets is investigated. The rotation rate dependence of the surface morphology and magnetic properties of the thin films were studied using atomic force microscopy combined with a magneto-optical measurement setup. The results show that decrease in the target rotation rate can also increase the roughness, the index of refraction, and the surface skewness and can decrease Faraday rotation by an order of magnitude. © 2010 Elsevier Ltd. All rights reserved.
Chinese Physics Letters (17413540) 27(12)
Nickel ferrite nanoparicles with various grain sizes are synthesized using annealing treatment followed by ball milling of its bulk component materials. Commercially available nickel and iron oxide powders are first mixed, and then annealed at 1100° C in an oxygen environment furnace and for 3 h. The samples are then milled fo different times in an SPEX mill. X-ray diffraction pattern indicates that in this stage the sample is single phase. The average grain size is estimated by scanning electron microscopy (SEM) and x-ray diffraction techniques. Magnetic behavior of the sample at room temperature is studied using a superconducting quantum interference device (SQUID). The Curie temperature of the powders is measured by an LCR-meter unit. The x-ray diffraction patterns clearly indicate that increasing the milling time leads to a decrease in the grain size and consequently leads to a decrease in the saturation magnetization as well as the Curie temperatures. This result is attributed to the spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core. © 2010 Chinese Physical Society and IOP Publishing Ltd.
Niyaifar m., ,
Beitollahi a., ,
Shiri n., ,
Mozaffari, M. ,
Amighian j., J. Journal of Magnetism and Magnetic Materials (03048853) 322(7)pp. 777-779
In this work we report the structure and magnetic properties of a series of single-phase indium-substituted yttrium iron garnet (In-YIG) nanoparticles with nominal composition of Y3InxFe5-xO12 (x=0.1, 0.2, 0.3 and 0.4) prepared by conventional mixed oxide route. Based on XRD results, the lattice parameters of the samples increased with increase in In3+ content due to its larger ionic radius. Mössbauer results confirmed the substitution of In3+ for Fe3+ in [a] site of YIG structure. Further, the magnitudes of the magnetic hyperfine field (MHF) were seen to reduce due to indium substitution. Moreover, a rising trend was observed for saturation magnetization (MS) of the samples with x>0.2 owing to the substitution of non-magnetic In3+ for Fe3+. However, the observed initial drop of MS for the sample with x=0.2 compared to that with x=0.1 is possibly attributed to the dominance of spin canting over the net magnetization rise caused by In3+ in [a] sites. © 2009 Elsevier B.V. All rights reserved.
Hasanpour, A. ,
Lehlooh, Abdel-Fatah D. ,
Motlagh Z.A. ,
Mozaffari, M. ,
Amighian j., J. ,
Lehlooh A.F. ,
Awawdeh M. ,
Mahmood S. Hyperfine Interactions (15729540) 198(1-3)pp. 295-302
A series of Al substituted yttrium iron garnet (Al-YIG) nanopowders with nominal formula of Y3Fe5-xAlxO12 which x varied in steps of 0.0, 0.5, 1.0, 1.5 and 2.0 were prepared via mechanochemical processing. The samples were milled for 40 h in a high energy planetary mill and then calcined at different temperatures from 1,300 to 1,100 degrees C. X-ray diffraction patterns reveal that the structure of nanopowders are bcc and the garnet phase has been obtained after calcining. The average crystallite sizes are in the range of 24-45 nm, using Scherrer's formula. The lattice constant of the samples decreases by increasing Al concentration. To investigate the site preference of Al3+ ions, room temperature Fe-57 Mossbauer spectra for the samples were recorded and analyzed. The hyperfine field values for octahedral and tetrahedral sites of the samples decrease by increasing x value. This decrease in magnetic hyperfine field reflects a reduction of the superexchange interaction by the progressive substitution of Al for Fe, which is also evident in the behavior of the magnetization and T-C for the samples.
Journal of Magnetism and Magnetic Materials (03048853) 322(18)pp. 2670-2674
A series of M-type strontium hexaferrite powders with substitution of Mn2, Ni2 and Ti4 ions for Fe3 ions according to the formula SrFe9(Mn0.5-xNi xTi0.5)3O19, where x ranges from 0 to 0.5 with a step of 0.1, has been prepared via the conventional ceramic method. In order to get nanoparticles, the obtained powders were milled in a high energy SPEX mill for 1 h. XRD investigations of the unmilled and milled powders show that the prepared samples are all single phase hexaferrite. Lattice parameters and mean crystallite sizes of the powders were determined from the XRD data and Scherrer's formula. Transmission electron microscope (TEM) was used to analyze their structures. Room temperature magnetizations and coercivities of the samples in a magnetic field of 15 kOe have been determined from the hysteresis loops. It was found that magnetizations of the milled samples were smaller than the magnetization of the unmilled samples. This decrease, based on coreshell model, has been attributed to the presence of a magnetically dead layer on the particles' surface of the milled powders. In addition, the magnetizations of the milled samples decrease with the increase in x value. This decrease has been discussed according to site occupation of the substituted cations on the sublattices. The discussion also supports the increase of lattice parameters and the decrease of Curie temperature as x increases. © 2010 Elsevier B.V.
Yousefi, M.H. ,
Manouchehri s., ,
Arab a., ,
Mozaffari, M. ,
Amiri, G.R. ,
Amighian j., J. Materials Research Bulletin (00255408) 45(12)pp. 1792-1795
Cobalt-zinc ferrite (Co0.8Zn0.2Fe2O 4) was prepared by combustion method, using cobalt, zinc and iron nitrates. The crystallinity of the as-burnt powder was developed by annealing at 700 °C. Crystalline phase was investigated by XRD. Using Williamson-Hall method, the average crystallite sizes for nanoparticles were determined to be about 27 nm before and 37 nm after annealing, and residual stresses for annealed particles were omitted. The morphology of the annealed sample was investigated by TEM and the mean particle size was determined to be about 30 nm. The final stoichiometry of the sample after annealing showed good agreement with the initial stoichiometry using atomic absorption spectrometry. Magnetic properties of the annealed sample such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 70 emu/g, 14 emu/g, and 270 Oe, respectively. The Curie temperature of the sample was determined to be 350 °C using AC-susceptibility technique. © 2010 Elsevier Ltd. All rights reserved.
Amin, M.M. ,
Khodabakhshi a., A. ,
Mozaffari, M. ,
Bina, B. ,
Kheiri, S. Environmental Engineering and Management Journal (15829596) 9(7)pp. 921-927
In this study, the efficiency of magnetic nanoparticles for removal of hexavalent chromium from simulated electroplating wastewater was evaluated. The nanoparticles were prepared using the sol-gel method and were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), a scanning electron microscopy energy dispersive X-ray analyzer (SEM-Edx), a particle sizer and a vibrating sample magnetometer (VSM). The results showed that synthesized nanoparticles were in the size range of 40-300 nm, had purity of about 90 percent, and had magnetization of 36.5 electromagnetic unit per gram (emu/g). In conditions including pH 2, Cr (VI) concentration of 10 mg/L, nanomagnetite concentration of 1 g/L, a shaking speed of 250 rpm and a 20 minute retention time, 82% of Cr(VI) was removed. Competition from common coexisting ions such as Na+, Ni2+, Cu2+, NO 3 -, SO4 2-, and Cl- was negligible. The adsorption data was well fitted by the Freundlich isotherm. It was concluded that magnetite nanoparticles have considerable potential for removal of Cr(VI) from electroplating wastewaters.
Journal of Magnetism and Magnetic Materials (03048853) 322(21)pp. 3240-3244
In this work zinc ferrite (ZnFe2O4) nanoparticles have been prepared by solgel method in two different media, one acidic and another one basic and then annealed at different temperatures from 350 to 800 °C. XRD investigations show that both samples have a single phase spinel structure. Mean crystallite sizes of the samples were calculated, using Scherrer's formula, which are 13 and 16 nm for the samples prepared in acidic and basic media, respectively. The variation of cation distribution in the samples was estimated by the ratio of (2 2 0) and (2 2 2) intensity diffraction peaks and the results show that as-prepared nanoparticles have different ionic distributions in comparison with that of bulk zinc ferrite. Also the results show that by increasing annealing temperature the ionic distribution of the zinc ferrite nanoparticles tends to that of bulk sample. The magnetic properties of the samples were studied by VSM and the results show that zinc ferrite nanoparticles have a ferrimagnetic behavior. Also the morphology of the powders was examined by TEM. © 2010 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 322(6)pp. 748-752
A series of La-substituted M-type Sr hexaferrite powders Sr1-xLaxTi0.05Zn0.2Fe3+ 11.75O19, wherein x ranges from 0.1 to 0.5 with a step of 0.1, have been prepared by the conventional ceramic method and were then milled in a high energy mill to prepare nanosized powders. XRD investigation of the calcined and the milled powders shows that single phase hexaferrite structure has been formed after calcining and has not changed after milling. The lattice parameters and the mean crystallite sizes of the samples have been determined from the XRD data and Scherrer's formula. The results show that the lattice parameters ("a{cyrillic}" and "c") decrease with increase in La-substitution and the mean crystallite size of the milled powders is about 17 nm. Coercivities and magnetizations of the samples in a magnetic field of 16 kOe have been determined from the room temperature hysteresis loops. It was found that both parameters increase with La substitutions up to 0.3 and then decrease for higher substitutions. These variations were attributed to the enhancement of hyperfine field and spin-canting magnetic structure when La content increases. In addition, the magnetizations were smaller for the nanosized samples in comparison with those of bulk ones, which were discussed according to the core-shell model. Also the results show that annealing of the nanosized samples up to 500 °C can enhance coercivity and magnetization of the samples, which is discussed based on crystallite size growth. © 2009 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 322(4)pp. 383-388
In this work zinc substituted cobalt ferrite nanoparticles (Co0.5Zn0.5Fe2O4) have been synthesized by the coprecipitation method, using stable ferric, zinc and cobalt salts with sodium hydroxide, at different solution temperatures, from room temperature to 363 K. The cobalt-zinc ferrite crystalline phase, the particle size and the morphology of the resulting nanoparticles were studied by X-ray diffraction and transmission electron microscopy. The average crystallite size of each sample was calculated from the broadening of the most intense peak (3 1 1), using Scherrer's formula and the results show crystallite sizes increased from 6 to 8 nm by increasing the solution temperature from room temperature to 363 K respectively. Room temperature VSM measurements show that the prepared nanoparticles have superparamagnetic behavior and did not saturate at maximum field of 800 kA/m. The variation of AC-susceptibility of the samples with respect to temperature was measured and it was found that the blocking temperature increased from 198 to 270 K by increasing the solution temperature from room temperature to 363 K respectively. FTIR spectra of the samples have been analyzed in the frequency range 400-4000 cm-1, which also confirms the results of XRD. © 2009 Elsevier B.V. All rights reserved.
Hasanpour, A. ,
Mozaffari, M. ,
Gheisari m., M. ,
Niyaifar m., ,
Amighian j., J. Journal of Magnetism and Magnetic Materials (03048853) 321(19)pp. 2981-2984
In this work, iron-wustite (Fe-FeyO) nanocomposites have been prepared via high-energy ball milling (HEBM), using high-purity hematite (alpha-Fe2O3) and iron (Fe) powders as the raw materials with different Fe/Fe2O3 mole ratios (MR) = 0.6, 0.9, 1.0, 2.3, 4.9 and 13.6. X-ray diffraction studies of the as-milled powders show that a single-phase wustite was formed for the lowest mole ratio (MR = 0.6) and mixtures with MRs higher than 0.6 result in iron-wustite nanocomposites, except for MR = 13.6 that is dominantly a pure iron phase. The mean crystallite sizes of the iron and wustite in the nanocomposites have been calculated by Scherrer's formula, which were 9+/-1 and 7+/-1 nm, respectively. Using the formula a = 3.856 + 0.478y, for FeyO, where a'' is the lattice parameter of wustite, it is possible to estimate the value of y'' for different nanocomposites and a composition of Fe0.93O was estimated for the wustite single-phase (MR = 0.6). In addition, a gradual decrease in y'' from 0.87 to 0.83 was obtained by increasing MR values from 0.9 to 4.9, respectively. The room-temperature Mossbauer spectrum of the single-phase wustite shows considerable asymmetry due to two overlapping quadrupole doublets. For higher MRs, room-temperature Mossbauer spectra exhibit sextets, which confirm the existence of iron in the samples. The Mossbauer spectrum of the sample with the highest mole ratio (MR = 13.6) shows only a sextet related to alpha-Fe without any detection of wustite, which is in agreement with the XRD results. The nanosized prepared wustite shows ferrimagnetic like behavior, which was interpreted according to spinel-liked defect clusters. The M-s values obtained from VSM measurements and those calculated based on the Mossbauer data and chemical reaction are in good agreement. By increasing MR from 0.6 to 2.3, the coercivity (H-c) increases sharply to its maximum value at about MR = 2.3, for which the value of Fe content is 45% and then drops off. This behavior is discussed based on alpha-Fe contents in the nanocomposites and percolation threshold. (C) 2009 Elsevier B. V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 321(9)pp. 1285-1289
A series of barium hexaferrite nanoparticles (BaO·nFe2O3) with different n values were prepared by the sol-gel method, using goethite and Ba carbonate as raw materials. Phase identification of the samples was investigated by X-ray diffraction (XRD). XRD investigations show that the samples with n=5 and calcined at temperatures higher than 875 °C are single-phase Ba ferrite. An average crystallite size of 22 nm was obtained for the single-phase sample with minimum calcining temperature of 875 °C, using the Scherrer's formula. The morphology of the samples was checked by transmission electron microscope (TEM) and magnetic properties were measured by a sensitive permeameter. The results show that the samples have nonzero coercivities, which shows the particle size are not less than the critical size of Ba ferrite and then are not superparamagnet. © 2009 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853) 321(13)pp. 1980-1984
The polycrystalline Y3Fe5-xAlxO12 compounds with x=0.5, 1.0, 1.5 and 2.0 were prepared by the mechanochemical method. The samples were milled for 40 h in a high-energy planetary mill and then calcined at different temperatures from 1300 to 1100 °C. The minimum calcination temperature to get a single phase garnet decreases by increasing Al concentration. X-ray diffraction patterns reveal that the structures of nano-powders are bcc and the garnet phase has been obtained after calcining. Also, the lattice constant of the samples decreases by increasing Al concentration,which is discussed based on the substitution of smaller aluminum ions instead of iron ions. The average crystallite sizes are in the range 24-35 nm using Scherrer's formula. The Curie temperature of single phase samples was found to decrease by increasing Al concentration, which can be discussed upon the reduction of magnetic interactions per magnetic ion. When more Al3+ is added, the magnetization is reduced because of the reduction of superexchange interactions in crystal lattice. © 2009 Elsevier B.V. All rights reserved.
Niyaifar m., ,
Ramani, ,
Radhakrishna m.c., ,
Mozaffari, M. ,
Hasapour a., ,
Amighian j., J. Hyperfine Interactions (15729540) 187(1-3)pp. 137-141
A series of Bi substituted yttrium iron garnet (Bi-YIG) nanoparticles with nominal formula of BixY3-xFe5O12 in which x varied in steps of 0.0, 0.25 and 0.5 are prepared by conventional method. Vibration sample magnetometer (VSM) at Room temperature (RT) shows saturation magnetization decreases from 27.4 to 25.2 (emu/g) as x value increases from 0.0 to 0.5. Room temperature 57Fe Mössbauer spectra are recorded for these series. The hyperfine field value for octahedral and tetrahedral of samples increases from 484 and 390 kOe to 491 and 397 kOe respectability, as Bi replaces Y in (BixY3-xFe5O12) atom with increasing x value. The effect of Bi3+ substitution for Y3+ on lattice constants, morphology and magnetic properties of pure YIG has been investigated. © Springer Science + Business Media B.V. 2008.
Hasanpour, A. ,
Mozaffari, M. ,
Gheisari m., M. ,
Mozaffari, M. ,
Acet M. ,
Amighian j., J. Journal of Magnetism and Magnetic Materials (03048853) 320(21)pp. 2618-2621
In this work wustite nanoparticles have been prepared via high-energy ball milling, using high-purity hematite (Fe(2)O(3)) and iron (Fe) powders as the starting materials. In order to get a single-phase wustite different mole ratios of (Fe/Fe(2)O(3)) were milled, using a planetary mill. X-ray diffraction studies of the as-milled powders show that a single-phase wustite was formed for a mole ratio of 0.6. Lattice parameter of the wustite was obtained from XRD data, by which a value of 0.072 was obtained for x in Fe(1-x)O. A mean crystallite size of 13 +/- 1 nm was calculated for the single-phase wustite, using Scherrer's formula. The morphology of the powders was also checked by TEM. Variations of pressure and temperature in the vial were recorded with respect to the milling time, using a GTM unit. Hysteresis loops of the as-milled powders at 5 K and room temperature have been obtained by SQUID and by VSM systems, respectively. The loops show non-zero coercivity, in contrast to the bulk wustite. The observed magnetizations can be explained by a model based on the spinel-type defect clusters in non-stoichiometry wustite. (C) 2008 Elsevier B.V. All rights reserved.
Journal of Alloys and Compounds (09258388) 449(1-2)pp. 65-67
Stoichiometric Mn1-xZnxFe2O4 (0 < x < 1) nanocrystalline powders in the range 25-35 nm in size were prepared via mechanochemical processing. The raw materials, Fe2O3 from a domestic source, MnO2 and ZnO, both from the Merck Company, were milled in a high-energy mill in air and annealed in various atmospheres and temperatures in order to achieve single-phase samples. Mean crystallite sizes of the annealed powders were calculated from XRD patterns, using Scherrer's formula. Magnetic measurements were performed on cold pressed samples and saturation magnetization was obtained. Also using an LCR-meter, the Curie temperature of each sample was measured. It was found that the minimum annealing temperatures for x = 0.2, 0.3, 0.4, 0.5, 0.6 and 0.75 were 950, 975, 1000, 1025, 1050 and 1100 °C, respectively. The results show that a single-phase nano-sized Mn-Zn ferrite can be achieved by annealing in an inert gas or vacuum. © 2006 Elsevier B.V. All rights reserved.
Niyaifar m., ,
Ramani, ,
Radhakrishna m.c., ,
Hassnpour a., ,
Mozaffari, M. ,
Amighian j., J. Hyperfine Interactions (15729540) 184(1-3)pp. 161-166
Magnetic and structural properties of Bi substituted YIG with nominal formula of Bi x Y3∈-∈x Fe5O 12 (x∈=∈0.0, 0.25, 0.5, 0.75, 1.00) prepared via Mechanochemical Processing (MCP) have been studied with Mossbauer spectroscopy, X-ray diffraction (XRD). The temperature dependence of sublattice magnetic hyperfine field for samples is analyzed. The a-d intersublattice superexchange found to be antiferromagnetic and increases from -∈21.97 to -∈25.79 kB as Bi increases from 0.0 to 0.25. The a-a and d-d intrasublattice exchanges for sample x∈=∈0.0 are 13.18 and 10.55 kB respectively while for sample x∈=∈0.25 a-a and d-d intrasublattice exchanges are 7.7 and 8.9 kB respectively. The correlation of lattice constant and superexchange interaction are discussed. © 2008 Springer Science+Business Media B.V.
Hasanpour, A. ,
Hasanpour, A. ,
Mozaffari, M. ,
Amighian j., J. ,
Richert H. ,
Lorenz A. ,
Lindner M. ,
Görnert P. ,
Heegn H. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (03048853) 317(1-2)pp. 41-45
Bi-substituted yttrium iron garnet with a composition of BiY2Fe5O12 (Bi-YIG) nanoparticles was prepared via mechanochemical processing and subsequent heat treatment. The maximum milling time was 8 h and the annealing was carried out at different temperatures up to 1000 degrees C for 4 h. Phase formation of the as-milled and annealed powders was investigated by X-ray diffraction (XRD). This investigation shows that there was no trace of garnet phase in the as-milled powder or the powders annealed below 800 degrees C. In the XRD patterns of the powders annealed above 800 degrees C, the peaks belonging to the garnet phase appeared and a single-phase garnet was finally obtained at 950 degrees C. Magnetic parameters of the powders were measured, using a SQUID unit, and a saturation magnetization of 22Am(2)/kg was obtained. Mean crystallite size of the single-phase powder, which was evaluated by Scherrer's formula was about 45 nm. Morphology of the powders was investigated by TEM, which shows that the particles were agglomerated. The single-phase powders were then dispersed in an organic binder for various Bi-YIG/binder weight ratios and for various dispersing times up to 80 h to obtain magnetic inks. Particulate films were made by the spin-coating method, using the magnetic inks. Magneto-optical properties (Faraday rotation) of the spin-coated films were investigated in the visible wavelength range of 470-625 nm. The results show that as Bi-YIG/binder weight ratios increases, the values of the Faraday rotation spectra increase too and their maximum values shift to shorter wavelengths. (c) 2007 Elsevier B. V. All rights reserved.
Physica B: Condensed Matter (09214526) 387(1-2)pp. 298-301
High-energy ball milling of Bi2O3 and Fe in air and argon atmospheres led to a novel Bi-Fe3O4 nanocomposite. XRD investigation of the as milled powder shows that there are only two phases of Bi and Fe3O4. GTM results show that the reaction is completed after about 2.5 h with no ignition temperature. Mean crystallite sizes of the Bi and Fe3O4 in the composite were 22 and 18 nm, respectively, calculated by Scherrer's formula. The morphology of the as milled powder was also investigated by a TEM. A two-probe method was used to measure resistivity variation of the composite as a function of temperature, by which a percolation temperature of 229 °C was obtained. © 2006 Elsevier B.V. All rights reserved.
Physica B: Condensed Matter (09214526) 371(2)pp. 309-312
The solid-state reduction of Bi2O3 to bismuth (Bi) nanoparticles by high-energy ball milling of raw materials (Bi2O 3 and Fe) in air and argon atmospheres has been described. XRD results show that in addition to bismuth, a second phase of nanocrystalline magnetite is also formed. This is due to the formation of Fe2O 3 and the subsequent change to Fe3O4 in the course of ball milling. Mean particle sizes of the obtained Bi and Fe 3O4 particles were 22 and 18 nm, respectively, using Scherrer's formula. A saturation magnetization of 80 emu/g is achieved for magnetic phase (Fe3O4). As both Bi and magnetite were nanosized particles, it was not possible to separate these two phases by the magnetic separation technique. A novel technique based on different thermal expansions of the Bi and Fe3O4 was then used to extract metallic Bi from the as-milled powders. © 2005 Elsevier B.V. All rights reserved.
Physica Status Solidi (C) Current Topics in Solid State Physics (16101642) 3(9)pp. 3188-3192
Nano-sized manganese ferrite (MnFe2O4) powder has been synthesized via coprecipitation method, using FeSO4̇7H 2O and MnSO4̇H2O as starting materials. An aqueous solution of the starting materials, containing Fe2+ and Mn2+ in the ratio required in the ferrite, was poured into an NaOH alkaline solution. A greenish precipitate was formed, which carefully washed and dried for 6 h at 80 °C. The dried powder was then heated for 2 h at different temperatures in argon atmosphere and then rapidly cooled to room temperature, using water quenching. XRD patterns of the samples show that the sample annealed at 1050 °C is single phase. Also using Scherrer's formula a mean crystallite size of 80 nm was obtained. Magnetic measurements were performed on cold pressed pellets, using a sensitive permeameter with a maximum field of 1.2 T. The results show that a single phase MnFe2O 4 nano-sized powder can be obtained at annealing temperature of 1050 °C, which is lower than 1250 °C related to the annealing temperature of the same ferrite, prepared by the conventional ceramic technique. Saturation magnetization of the single-phase sample was 1330 G, which is lower than 5000 G related to a bulk sample. The difference between the values is reasonable, because the magnetic measurements were performed on cold-pressed unsintered nano sized powders. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
Hasanpour, A. ,
Lehlooh, Abdel-Fatah D. ,
Lehlooh A.F. ,
Mahmood S. ,
Mozaffari, M. ,
Amighian j., J. Hyperfine Interactions (15729540) 156(1)pp. 181-185
Room-temperature Mossbauer spectra were recorded for two series of Al-Cr co-substituted rare-earth iron garnets: YIG (Y3AlxCrxFe5-2xO12) and Y-GdIG (Y(1.)5Gd(1.5)Al(x)Cr(x)Fe(5-2x)O(12)). All the spectra were fitted with two magnetic sextets, one sextet corresponds to the (a) octahedral site and the other corresponds to the (d) tetrahedral site. The hyperfine fields for all the samples show a reduction of (similar to5 Tesla) per substituted atom with increasing x. The values of the hyperfine fields of the Y-GdIG samples are slightly higher than those of the YIG samples. The relative intensities of the two sextets show that upon substitution, the Al-Cr occupy the (a) site rather than the (d) site. Also, the line widths of the two sextets were found to increase systematically upon substitution, due to the increasing atomic disorder as the Al-Cr contents increase.
Physica Status Solidi C: Conferences (16101634) 1(7)pp. 1769-1771
A series of Bi substituted yttrium iron garnet (Bi-YIG) nanoparticles with nominal formula of BixY3-xFe5O12, in which x varied in the steps of 0.0, 0.5, 1.0 and 1.5, were prepared via mechanochemical processing (MCP). A milling time of 5 hours was found to be suitable for all the samples. Minimum annealing temperature for completion of the phase formation was determined for each sample. The optimum annealing temperature of each sample is much lower than the annealing temperature for the completion of the related phases in the conventional ceramic technique. The average sizes of the particles were determined by Scherrer's formula and were in the range of 30 nm to 40 nm. The effect of Bi3+ substitution for Y3+ on lattice parameters and magnetic properties of pure YIG has been investigated. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Journal of Magnetism and Magnetic Materials (03048853) 260(1-2)pp. 244-249
Single-phase NiAlFeO4 fine particles were prepared via high-energy ball milling (HEBM) and subsequent heat treatments. X-ray diffraction (XRD) of the as-milled powder indicates that a dominant spinel phase forms after 60h of milling. A complete single phase of NiAlFeO4 was formed by subsequent heat treatments of the as-milled powder at 950 °C, which is lower than the temperature associated with the conventional ceramic technique. XRD, EDS, DTG/M/ and magnetic observations were used to discuss mechanism of the ferrite formation by HEBM and subsequent heat treatments. © 2002 Elsevier Science B.V. All rights reserved.
Physica B: Condensed Matter (09214526) 321(1-4)pp. 45-47
Mineral celestite was directly used to prepare presintered single-phase Sr-ferrite powders for fabrication of sintered permanent magnets. The starting materials were high-purity domestic celestite, modified iron oxide and sodium carbonate. The role of sodium carbonate is firstly to promote the displacement solid-state reaction and secondly to lower the temperature during calcining stage. A vibrating sample magnetometer was used to measure magnetic parameters of the powders. The results were compared with those of the powders prepared by conventional ceramic process. Lower reaction temperature of 1000 °C and low-cost celestite show that this process is more economical for production of presintered SrFe12O19 powders than the conventional one. © 2002 Elsevier Science B.V. All rights reserved.
