جستجوی مقالات مرتبط با کلیدواژه « magnetic properties » در نشریات گروه « مواد و متالورژی »

In recent years, there has been a significant interest in lanthanum-based perovskites due . Lanthanum strontium manganite (LSMO) is one of the most well-known materials. In this research, the synthesis and investigation of the effect of oleic acid on the structural and magnetic properties of La0.7Sr0.3MnO3 nanoparticles by the combustion sol-gel method is discussed. The structural and magnetic properties of the prepared samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), magnetic properties analysis (VSM), and field emission electron microscopy (FESEM). In the XRD study, it was found that the crystal structure of the samples is hexagonal. Also, the average crystal size in the samples increased from 18 nm to about 33 nm as a result of adding oleic acid. The images obtained from FESEM show that the presence of oleic acid in the synthesis of nanoparticles caused it to affect the shape of the particles as a surface layer. Synthesized nanoparticles have a particle size between 20-100 nm, and with the increase of oleic acid, the particle size becomes more than 100 nm. FTIR spectroscopy revealed the effective bonding between LSMO nanoparticles and oleic acid, based on these results, it clearly shows the presence of oleic acid molecules on the surface of magnetic particles. In the investigation of magnetic properties, it was found that the presence of non-magnetic sodium oleate surface layer, which due to the addition of oleic acid on nanoparticles, the saturation magnetization value decreased from 38.55 emu/g to 28.46 emu/g.

Iron oxide nanoparticles have been gaining much attention lately due to their magnetic properties and biocompatibility. This research focused on investigating the properties and synthesis of iron oxide nanoparticles that have been substituted with zinc ZnxFe3-xO4 (x= 0.0, 0.2, 0.4, 0.6)  using the hydrothermal method. The synthesized samples were analyzed using X-ray diffraction and found that they have a space group of fd3m. The crystal size of the samples was found to be smaller than 20 nm. Vibrating sample magnetic analysis (VSM) was used to determine the magnetic behavior of the nanoparticles. The analysis showed that the nanoparticles exhibited superparamagnetism. In addition, the saturation magnetization values of the nanoparticles for samples with x = 0, 0.2, 0.4, and 0.6 were 44.10, 49.09, 43.51, and 48.07 emu/g, respectively. The microstructure and grain size of magnetic nanoparticles were analyzed using a field emission electron microscope (FESEM). The FESEM images revealed that the majority of the grains are spherical and have uniform distribution. The average grain size for the sample ranges between 10 and 30 nm. Based on these results, it can be concluded that these particles are suitable for use in medical and catalytic applications.

In the current research, Nd2(Fe,Co)14B hard magnetic nanoparticles were synthesized through the reduction diffusion process. For this purpose, Nd(Fe1-xCox)B oxide powders for x = 0.05, x = 0.3, and x = 0.5 were heat-treated once in hydrogen atmosphere (H2) and once in the reduction diffusion process using calcium hydride (CaH2). The phase analysis and chemical composition of the resulting Nd-Fe-Co-B powders were identified by X-ray diffraction and X-ray energy dispersive spectroscopy. The morphology and magnetic properties of the synthesized powders were investigated using a field emission scanning electron microscope, transmission electron microscope, and vibrating sample magnetometer. The results demonstrated that oxide powders reduced with hydrogen gas were characterized by a soft magnetic character due to the formation of the bcc-FeCo magnetic phase. However, oxide powders reduced via reduction diffusion exhibited hard magnetic characteristics due to the direct diffusion of NdH2, Fe, Co, and B phases as well as the production of Nd2(Fe,Co)14B hard magnetic phase. The Nd2(Fe,Co)14B particles were rinsed with water and dilute acetic acid to eliminate the byproducts (CaO) formed during the reduction diffusion process. Followed by washing, coercivity dropped due to the formation of the Nd2Fe14BHx soft magnetic phase; however, saturation magnetization rose due to the elimination of the non-magnetic CaO phase from the final production.

The goal of this study was the investigation of the structural and magnetic characteristics of MnBi permanent magnets. In this regard, the mechanical milling and annealing processes were used for the synthesis of Mn45Bi50M5 (M= Sb, Ge, B) samples. Based on the results, the best annealing temperature and time for the formation of the highest value of MnBi ferromagnetic phase with optimum magnetic properties (Hc=1750 Oe and Ms= 12 emu/g) were recognized at 325 oC and 24 h, respectively. B, Ge, and Sb elements had a distractive effect on the stabilization of the MnBi ferromagnetic phase. Consequently, the samples containing B, Ge, and Sb showed lower magnetic characteristics in comparison with the Mn50Bi50 stoichiometric sample.

Cobalt ferrite is a magnetic material with a spinel structure. nano particles of Cobalt ferrite is attractive because of medium supersaturation, magnetic anisotropy,optical properties which causes to wide range applications such as drag delivery, cancer diagnosis and treatment, magneto-sensor, optical fibers and magneto-optical devices. In this investigation, the effect of reaction temperature on structure and magnetic properties of co-precipitated cobalt ferrite nanoparticles was studied. The nanoparticles were synthesized at 80, 90,100 and 110 C. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibration sample magnetometer (VSM) were used to charactization of nano particls. The results showed that cobalt ferrite nanoparticles was synthesized at all the reaction temperatures and supersaturation of non-calcination samples was noticeable. According to the results, by increasing the reaction temperature, crystallite size increased from 32 nm to 90 nm and also the magnetic supersaturation increased from 32 from 71.5 emu/g. besides, The purity of cobalt ferrite increased with increasing reaction temperature.

Nanoparticles are comprised from dozens or hundreds of atoms or molecules with different sizes and morphologies are being applied widely due to their unique properties in chemistry, physic, and biology. Multiferroic compounds have been considered significantly owing to their applications arising from their ferromagnetic, ferroelectric, and fibroelastic properties. Among all multiferroic compounds, ferrite bismuth (BiFeO3) has attracted remarkable attentions which is a weak pad-ferromagnetic in the magnetic points of view. Of the best impressive approaches for improving its properties is the substitution of the metals including La, Ba, Pd, Sr, and Ca in A positions or Ti, Cr, and Mn in B positions through BiFeO3 scaffold. In this work, Bi1-XLaxFeO3 and Bi0.9-YLa0.1BaYFeO3 nanoparticles were synthesized and the structural and magnetic properties of synthesized nanoparticles were also studied.BiFeO3 particles were synthesized by mixing the Bi(NO3)3.5H2O, La(NO3)2.6H2O, Ba(NO3)2.4H2O, and Fe(NO3)3.9H2O precursors in nitric acid in the presence of surfactants Saponin, Triton CG-100, Crocin, or N-octyl-beta-D-glucoside and tetraethylenepentamine as base.

Zinc-cobalt ferrite nanoparticles (NPs) were synthesized using co-precipitation method. In the present process, NPs precipitated at various pHs, then calcined at 750°C for 2 h. X-ray diffraction (XRD) analysis confirmed single phase of ZnCo ferrite phase in all of the samples. Williamson-Hall calculations showed that the strain value in the microstructure of specimen prepared at pH= 8 is equal to -7*10-4. This content for pHs of 11 and 14 increased to 10-4 and 10-3, respectively. Therefore, the highest crystallite diameter was obtained as 51.35 nm for prepared NPs at pH= 14. Field emission scanning electron microscopy (FESEM) showed a relatively uniform distribution of particles with average size of 9.38, 50.1 and 30.7 nm for prepared powders at pHs equal to 8, 11 and 14, respectively. Vibrating sample magnetometer (VSM) measurements revealed that saturation magnetization (MS), anisotropic constant (K) and Bohr magneton (nB) characteristics are different at various pHs. So that, these parameters were obtained as 95.48 emu/g, 14.614*103 and 4.06, respectively for prepared powders at pH= 8, while at pH= 11 increased to 100.34 emu/g, 15.358*103 and 4.27, then changed to 81.98 emu/g, 11.712*103 and 3.49 at pH= 14. It was found different conditions of particles precipitation have a remarkable role on the properties of produced NPs.

In this research, spinel ferrite (CuFe2O4) magnetic nanoparticles were synthesized by the solvothermal approach in the polyol media and used for the adsorptive removal of Reactive Red 141 (RR 141) as a model of organic dye. Batch adsorption studies were carried out for various pH values, nanoadsorbent loadings, contact times, temperatures, and initial concentrations of the organic pollutant. The adsorption isotherms were in the range of 10–50 ppm and the results fitted well with Langmuir isotherm. The sorption kinetic studies well-defined to Ho’s pseudo-second order model. This research suggests an effective low cost CuFe2O4 nanoadsorbent with a reasonably high efficiency for the removal of RR141 compound, which allows convenient recovery from aqueous media using a weak external magnetic field.

Strontium hexaferrite M-type nanoparticles doped with La and Cu (SrFe12-xCuxO19-Sr1-xLaxFe12-xCuxO19) with different mole fractions (x=0.1-0.2-0.3-0.4-0.5) synthesized by self-combustion sol-gel technique. Firstly, a gel of metal nitrates with the above-mentioned mole fractions were fabricated and the obtained powder was cured at 950°C. Microstructural properties and the morphology of the compounds were investigated by employing X-ray diffraction (XRD) and scanning electron microscopy (SEM). Also, in order to investigate the magnetic properties, Vibrating Sample Magnetometer (VSM) was used. SEM images revealed that the particles had an average size of about 100 nm. Cu2+ ions were substituted with Fe3+ ions within the crystalline sites of SrFe12O19 structure. It was shown that the lattice parameter (a) remained approximately unchanged with an increase in Cu-dopped while the lattice parameter (c) decreased with increasing the mole fraction (x). By using VSM hysteresis diagrams, it was observed that the saturated magnetization and coercive force increased with the addition of La; this was attributed to the variation in the distribution of ions and the shape anisotropy of the nanoparticles. These significant changes in the magnetic properties were for the sample with the composition of Sr1-xLaxFe12-xCuxO19 and SrFe12-xCuxO19, for the x=0.1 and x=0.5, respectively.

Mn0.8Zn0.2Fe2-xDyxO4 (where x= 0, 0.025, 0.05, 0.075, 0.1) ferrite nanoparticles were synthesized by auto- combustion sol-gel method for the first time in this study. The effect of Dy-doping on the structural and magnetic properties of the produced specimens was examined using the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometery (VSM), and field emission scanning electron microscope (FE-SEM). The results showed that a cubic spinel structure was formed in all of the synthesized specimens. It was also found that the addition of Dy increased the lattice parameter while decreased the average of crystallites size. Furthermore, the FE-SEM micrographs showed that Dy not only plays an effective role in reducing the agglomeration of nanoparticles and their distribution, but also reduces the average of particle size. It was also observed that the addition of Dy had no effect on the morphology of the synthesized nanoparticles. Investigation of the magnetic properties revealed a clear decrease in the saturation magnetization and coercivity by the Dy addition. So that the saturation magnetization of the samples decreased from 66.3 to 58.4 emu/g and the coercivity decreased from 78.5 to 71.9 Oe.