Showing 14 results for Subject: Electronic and magnetic materials
M. Hosseinzadeh, M. Bozorgmehr, M. Askari,
Volume 36, Issue 1 (6-2017)
Abstract
Cobalt-based amorphous alloys attracted the attention of many researchers to carry out fundamental research for their application in electronics, sensors and magnetic memory due to their special magnetic properties including close to zero Magnetostriction, magnetic permeability and high saturation magnetization. The purpose of this study is the formation and evaluation of microstructure and magnetic properties of cobalt-based amorphous alloy produced by melt spinning and mechanical alloying. The final compositions produced by both methods were studied by scanning electron microscopy, X-ray diffraction and vibrating magnetoresistance. The results showed that compound produced by chill block melt spinning has a better magnetic properties.
S. S. Seyyed Afghahi, M. Jafarian,
Volume 36, Issue 1 (6-2017)
Abstract
In this study, the effect of Fe/Ba molar ratio was investigated on the phase composition, synthesis temperature, microstructure and magnetic properties of barium hexaferrite prepared via mechanical activation. In order to synthesize this compound, Fe/Ba molar ratios of 12 and 6 were used. The effect of Fe/Ba molar ratio, milling time and heat treatment temperature for achieving the optimal conditions in producing this compound was studied. In order to study the phase, morphology and magnetic properties of the final product, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM) were used respectively. According to the results, Fe/Ba molar ratio of 6, 10 h milling time and temperature of 800 °C were found to be the optimal conditions for producing this compound in a single phase. Scanning electron microscopy images show the hexagonal morphology and almost spherical particles respectively for samples prepared with Fe/Ba molar ratio equal to 12 and 6. Moreover, according to the magnetic studies, the maximum amount of saturation magnetization (56.48 emu/g) and the coercivity force (5247.2 Oe) were obtained for the sample synthesized with Fe/Ba molar ratio of 6.
A. Rostamnejadi, M. K. Esmaeilzadeh,
Volume 36, Issue 3 (11-2017)
Abstract
In this research, nanoparticles of La0.8Sr0.2MnO3 with mean crystallite size of 20 nm have been prepared by sol gel method. The sample has been characterized by X-Ray Diffraction (XRD) using Rietveld refinement, Field Emission Scanning Electron Microscope (FESEM) and Fourier Transform Infrared (FTIR) spectroscopy. The static magnetic properties such as saturation magnetization, effective magnetic moment and ferromagnetic phase fraction of the nanoparticles are determined by different techniques using magnetic hysteresis loop at room temperature. The magnetic dynamic properties of crystalls are studied by measuring AC magnetic susceptibility versus temperature at different frequencies. Néel-Brown, Vogel-Fulcher, critical slowing down models and empirical parameters are used to distinguish between superparamagnetic and superspin glass behaviour in the nanoaprticles. By fitting the experimental data with the models, relaxation time, critical view, magnetic anisotropy energy and effective magnetic anisotropy constant have been estimated. The obtained results support the presence of interacting superparamagnetic behaviour between magnetic nanoparticles of La0.8Sr0.2MnO3.
Mrs M. Amoohadi, Mr M. Mozaffari, A. R. Gharaati, M. Rezazadeh,
Volume 37, Issue 1 (6-2018)
Abstract
In this study, iron powder (~45 μm) with the minimum purity of 99% was insulated by the 1 to 4 wt% sodium silicate insulator (SiO2.3Na2O solution in 40 wt% water) and the 0.5 wt% zinc stearate. Insulated powders were pressed in a die with a toroidal shape at the pressure of 320 MPa. The effects of insulator percentage and annealing temperature on the magnetic permeability, core loss tangent, and the total loss were investigated. The results indicated that the sodium silicate insulator could be suitable for insulating iron powders used in iron powder cores for high frequencies up to 1000 kHz. Also, this insulator could be stable against heat up to 450 °C.
M. Hosseinzadeh, M. Bozorgmehr, A. Ghasemi, M. Askari,
Volume 37, Issue 2 (9-2018)
Abstract
NdFeB magnetic alloy is one of the hard magnets having the highest maximum energy in the world. The most popular methods of manufacturing magnetic alloys Nd2Fe14B are powder metallurgy and rapid quenching techniques. In this research, the effect of the hot press temperature on the magnetic properties of the hard magnet Nd2Fe14B was studied. Structural studies were carried out using X-ray diffraction, X-ray fluorescence spectrometer and Scanning Electron Microscope; Spectroscopic energy distribution of Nd2Fe14B bulk magnet and the magnetic tests were done using a vibrating magnetometer to investigate the structures and the magnetic properties of the produced samples. The results showed that in addition to the Nd2Fe14B phase, the α-Fe and Nd-rich phase also existed in the structure of the provided magnet. These secondary phases had effectively created exchange couplings with the main phase, improving the magnetic properties. The magnetic properties of the sintered magnets were improved by increasing the press temperature; finally, Nd2Fe14B magnet was made with the maximum energy, which was d higher than 290 kj/m3 .
A. Baradaran, M. Tavoosi,
Volume 37, Issue 3 (12-2018)
Abstract
In the present study, the structural, optical and thermal behaviors of GeO2-PbO-CaO-SrO glasses were investigated to achieve the highest optical properties and thermal stability. Accordingly, different 50GeO2-(50-x)PbO-xCaO and 50GeO2-(50-x)PbO-xSrO (x=0, 10, 20) germanate glasses were prepared by the conventional melt and quench technique between two steel sheets. The produced samples were characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. Based on the obtained results, the addition of CaO to glass composition reduced the glass phase forming ability as well as optical and thermal behaviors of the prepared glasses. In contrast, the presence of SrO had no destructive effect on the optical properties of the prepared glasses; the highest values of glass transition (580 oC) and crystallization temperature (831 oC) were achieved in the sample containing 20 mole% of SrO.
M. Hakimi, M. Safari,
Volume 38, Issue 1 (6-2019)
Abstract
In this study, the improvement of the magnetic properties of Co2FeSi Heusler compound was followed by the utilization of different experimental synthesizing procedures. Comparing the crystal structure showed that the milled samples had a higher crystalline order than the arc-melted ones. Annealing of the milled sample improved the crystalline order, resulting in the highest saturation magnetization (5/24 μB/F.u.). The difference in the saturation magnetization of the other samples was explained by the core-shell model. Comparison of the various coercivity mechanisms showed that the decrease in the size of crystallites played a key role in the higher value of the milled samples coercivity.
H. Salehi, N. Zhulayi Bakhoda, P. Amiri,
Volume 38, Issue 4 (1-2020)
Abstract
In this research, the optical properties of tungsten disulfide including dielectric function, the static refractive index, the imaginary part of the dielectric function, optical band gap, energy loss spectrum and its magnetic properties have been studied. Calculations have been done by using Quantum Espresso package which is based on density functional theory and pseudo-potential technique. The static refractive indices of this compound at diffrent x and z directions were calculated 3.66 and 2.55, respectively. The amount of optical band gap, obtained from the imaginary part of dielectric function, was estimated to be 1.45 eV. In addition, bulk plasmon energy, obtained from energy loss spectrum at x and z directions, were obtained to be 17.95 eV and 17.25 eV, respectively.
Kh. Zamani, M. Tavoosi, A. Ghasemi ,
Volume 39, Issue 4 (2-2021)
Abstract
In this research, effect of B and Si addition on the structural and magnetic properties of AlCoCrMnNi high-entropy alloys was investigated. The structural and magnetic properties of AlCoCrMnNiX(X= B, Si) alloys were studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). First, the constituent components of the AlCoCrMnNiX (X=B, Si) alloys were mixed for 10 hours. XRD analysis revealed that the solid solution was not formed by mixing. The alloys were then annealed at 900 ˚C for 10 hours. XRD results revealed formation of a solid solution with BCC structure in AlCoCrMnNi and AlCoCrMnNiB alloys. For AlCoCrMnNiSi and AlCoCrMnNiSiB alloys, Ni2Si and Cr2Si3 intermetallics were formed in addition to the solid solution with BCC structure. VSM results suggested that while forming the solid solution for AlCoCrMnNi alloy, soft magnetic properties improved so that magnetic saturation and coercivity increased from 40.22 to 64.46 emu/g, and from 180.143 to 14.09 Oe, respectively.
S. Sarafrazian, M. Tavoosi, A. Ghasemi ,
Volume 40, Issue 2 (9-2021)
Abstract
The aim of this study was optimization of the annealing process in melt spun Nd2Fe14B intermetallic magnetic alloy. In this regard, the melt spinning process was done at wheel speed of 40 m.s-1. In order to achieving the desired microstructure, the as-spun ribbons were subsequently annealed at temperature range of 500 to 700 ºC for different periods of time. Structural and magnetic characterization of produced samples were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results showed that the structure of as-spun ribbons at wheel speed of 40m.s-1 was composed of Fe-α, Nd2Fe14B and amorphous phases with the coercivity and saturation of magnetization in the range of 0.14 kOe and 120 emu/g, respectively. By annealing the produced ribbons and crystallization of the amorphous phase, the percentage of Fe-α and Nd2Fe14B was decreased and increased, respectively. The optimum annealing conditions for achieving the highest value of coercivity (about 9.2 kOe) was 600°C for 6h.
H. Fallah-Arani, S. Baghshahi, A. Sedghi, F. Shahbaz Tehrani,
Volume 40, Issue 2 (9-2021)
Abstract
In this research, the influence of titanium dioxide nanoparticles on the structural and magnetic properties of high-temperature superconductor Bi1.6Pb0.4Sr2Ca2Cu3O10+θ (Bi-2223) from the Bi-based ceramic system (BSCCO) was studied. In order to investigate the synthesized samples, X-ray diffractometry and magnetic measurements were performed. Based on the magnetic measurements, the superconductivity transition temperature declined with the increase in the nanoparticles' content. The addition of nanoparticles affected on the hysteresis loop width. Accordingly, the compound containing 0.2 wt.% nanoparticles had the maximum magnetization, hysteresis loop width, and critical current density.
M. Ghorbani, H. Khorsand,
Volume 40, Issue 2 (9-2021)
Abstract
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.
N. Ghobadi, S. A. Hosseini Moradi, M. Amirzade,
Volume 40, Issue 4 (3-2022)
Abstract
In this research, cobalt ferrite powders (CoFe2O4) and cobalt ferrite/reduced graphene oxide composite (CoFe2O4/RGO) were synthesized by the co-precipitation method. The phase structure, morphology, magnetic properties, and microwave absorption properties of the produced samples were investigated through various techniques. X-ray diffraction test indicated the successful formation of pure CoFe2O4 and its composites with RGO. According to the Scanning electron microscopy (SEM) images, most pure and composite samples’ particles were formed in a semi-spherical shape. The VNA test results showed the saturation magnetization of CoFe2O4 and the composite containing 5 wt.% and 10 wt.% of RGO, 71.6, 56, and 37 emu/g, respectively. Also, the network analyzer results demonstrated the maximum reflective losses in the X-band range due to the impact of microwaves on CoFe2O4 te was -5.5 db. This amount reached 21.5 dB with the addition of 10 wt.% RGO. Also, the wave input increased from 41% for the pure CoFe2O4 to 99.5% for the sample containing 10 wt.% RGO.
Sh. Talebniya, M. R. Saeri, I. Sharifi, A. Doostmohammadi,
Volume 41, Issue 1 (8-2022)
Abstract
Magnetic nanoparticles are of interest in various research fields such as magnetic fluids, catalysts, biotechnology, medicine, information storage, and environmental issues. However, spinel ferrite magnetic nanoparticles with proper magnetic properties could not be used alone in these applications because of their lack of biocompatibility and instability in aqueous solutions. Surface coating is an effective strategy to eliminate or minimize this issue. In this study, FeFe2O4 and ZnFe2O4 spinel ferrites were synthesized using the reverse co-precipitation method under a nitrogen gas atmosphere. The magnetic behavior of the particles, determined by a vibrating magnetometer (VSM) showed the saturation magnet (Ms) values of the FeFe2O4 and ZnFe2O4 spinel. Fourier-transform infrared (FTIR) spectra showed two high-frequency bands v1 and v2 at about 554-578 and 368-397 cm-1, respectively, which were related to the spinel structure. Finally, the synthesized FeFe2O4 nanoparticles were coated with chitosan and polyethylene glycol (PEG) biopolymers. The TEM and FTIR analysis indicated that the magnetic nanoparticles were uniformly coated by the biopolymers.
