Showing 9 results for Magnetic Properties
Z. Ghiami, S. M. Mirkazemi, S. Alamolhoda,
Volume 12, Issue 2 (6-2015)
Abstract
trontium hexaferrite (SrFe
12
O
19
) nanosized powders were synthesized by sol-gel auto-combustion method
with and without cetyltrimethylammonium boromide (CTAB) addition in the sol with Fe/Sr ratio of 11 (using additional
Sr). The resultant powders were investigated by X-ray Diffraction (XRD), Transmission Electron Microscope (TEM),
Field Emission Scanning Electron Microscope (FESEM) and Vibration Sample Magnetometer (VSM) techniques.
Phase constituents of the synthesized samples which were heat treated at temperatures in the range of 700- 900 ◦C
were studied. XRD results revealed that CTAB addition facilitates the formation of single phase strontium hexaferrite
at 800 ◦C. Microstructural evaluations with FESEM represented that CTAB addition causes formation of larger
particles with a narrower size distribution. VSM results represented that the highest amount of intrinsic coercivity force
(
i
H
C
) was obtained in the sample without CTAB addition and with additional Sr, calcined at 800 ◦C for 1 h which was
equal to 5749.21 Oe, while the value of
i
H
C
was equal to 4950.89 Oe without additional Sr. The amount of maximum
magnetization (M
max
) was raised from 48.41 emu/g to 62.60 emu/g using CTAB and additional Sr. The microstructure
and magnetic properties of the samples have been explained
S. Alamolhoda, S. M. Mirkazemi, T. Shahjooyi, N. Benvidi,
Volume 13, Issue 1 (3-2016)
Abstract
Nano-sized NiFe2O4 powders were synthesized by sol–gel auto-combustion method using pH values from 7 to 9 in the sol. The effect of pH variations on complexing behavior of the species in the sol has been explained. Changes in phase constituents, microstructure and magnetic properties by changes in pH values were evaluated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. Changes in pH value from 7 to 9 changes the amounts of NiFe2O4, FeNi3 and α-Fe2O3 phases. Calculated mean crystallite sizes are in the range of 44 to 51nm. FESEM micrographs revealed that increasing the pH value to 9 causes formation of coarse particles with higher crystallinity. Saturation magnetization was increased from 36.96emu/g to 39.35emu/g by increasing pH value from 7 to 8 which is the result of increased FeNi3 content. Using higher pH values in the sol reduces the Ms value.
B. Pourgolmohammad, S.m. Masoudpanah, M.r. Aboutalebi,
Volume 15, Issue 2 (6-2018)
Abstract
In this work, the different fuels (citric acid, glycine and urea) were used for solution combustion synthesis of CoFe2O4 powders. X-ray diffraction, Raman spectroscopy, electron microscopy and vibrating sample magnetometry techniques were employed for characterization of phase evolution, cation distribution, microstructure and magnetic properties of the as-combusted CoFe2O4 powders. Single phase CoFe2O4 powders with partially inverse structure in which the Co2+ cations are distributed in both tetrahedral and octahedral sites were synthesized by the citric acid, glycine and urea fuels. The as-combusted CoFe2O4 powders by the citric acid fuel exhibited the highest inversion coefficient. The crystallite size of the as-combusted CoFe2O4 powders synthesized by urea fuel was 15 nm, increased to 41 and 52 nm for the glycine and citric acid fuels, respectively. Furthermore, the solution combusted CoFe2O4 powders showed ferromagnetic behavior with saturation magnetization of 61.9, 63.6 and 41.6 emu/g for the citric acid, glycine and urea fuels, respectively. The high crystallinity and particle size of the as-combusted CoFe2O4 powders using glycine fuel led to the highest magnetization and the moderate coercivity.
S. Mirzaei, H. Saghafian, A. Beitollahi, J. Świerczek, P. Tiberto,
Volume 16, Issue 3 (9-2019)
Abstract
In the present research, rapidly solidified Fe85.3B11P3Cu0.7 ribbons were prepared by melt spinning process. The microstructural variation as well as magnetic properties of the as-spun and annealed ribbons were characterized by X-ray diffraction (XRD), transmission Mossbauer spectroscopy and alternating gradient field magnetometer (AGFM). The results show two separated distinct exothermic peaks during heating resulting from the phase transition from amorphous to α-Fe and then to Fe3B, respectively. The study of magnetic properties in the amorphous and nanocrystalline states revealed that annealing the amorphous ribbons at 440˚C for 10 minutes gives rise to a significant increase in saturation magnetization (220 emu/g) which makes this alloy a good candidate for power applications.
Ehsan Tarighati, Majid Tavoosi, Ali Ghasemi, Gholam Reza Gordani,
Volume 19, Issue 1 (3-2022)
Abstract
In the present study, the effects of boron on the structural and magnetic properties of AlCrFeNiMnSiBx high entropy alloys (HEAs) were investigated. In this regards, different percentages of boron element were added to the based composition and the samples were identified using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Based on results, the tendency of Si element to formation of silicide phases prevents from the stabilization of single FCC and BCC solid solution phases in AlCrFeNiMnSi alloy. The boron element has significant effects on destabilization of silicide phases and by increasing in the percentage of this element, the simple BCC solid solution phase has been dominate phase. Of course, boron has distractive effects on magnetic properties of prepared alloys and the saturation of magnetization of AlCrFeNiMnSiBx HEAs decrease from 29.8 emu/g to about 6 emu/g by increasing the boron content.
Parisa Rastgoo Oskoui, Mohammad Rezvani, Abbas Kianvash,
Volume 20, Issue 2 (6-2023)
Abstract
Abstract
The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of 20SiO2.50FeO.30CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at 25℃ with a precursors to solvent ratio of 1/5. After aging the resulted gel for 24 h at room temperature, it was dried in an electric dryer at 110 ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were 360℃ and 440℃ respectively. By increasing the heat treatment temperature to higher than 440℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (1.9 emu/g) belonged to sample heat treated at 680℃ . By increasing the heat treatment temperature to 840℃ , the magnetization decreased to 0.8 emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from 440℃ to 680℃ , crystalline size of maghemite was increased from 40 to 200 nm. By forther increment of temperature to 840℃ , the size of maghemite crystals decreased to 17nm, due to the oxidation of maghemite to hematite.
Abstract
The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of 20SiO2.50FeO.30CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at 25℃ with a precursors to solvent ratio of 1/5. After aging the resulted gel for 24 h at room temperature, it was dried in an electric dryer at 110 ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were 360℃ and 440℃ respectively. By increasing the heat treatment temperature to higher than 440℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (1.9 emu/g) belonged to sample heat treated at 680℃ . By increasing the heat treatment temperature to 840℃ , the magnetization decreased to 0.8 emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from 440℃ to 680℃ , crystalline size of maghemite was increased from 40 to 200 nm. By forther increment of temperature to 840℃ , the size of maghemite crystals decreased to 17nm, due to the oxidation of maghemite to hematite.
Elham Ghasemi, Majid Tavoosi, Ali Ghasemi, Mohammad Loghman Estarki,
Volume 20, Issue 2 (6-2023)
Abstract
In the present study, the structural and magnetic characteristics of Fe-Co-Cr system, with 28 at. % of Cr content, during casting, solutioning and thermo-magnetic treatment has been investigated. Based on results, the formation of single α-phase solid solution in the Fe72-xCoxCr28 (10The Co content had negligible effects on magnetic characteristics of Fe62Co10Cr28, Fe60Co12Cr28 and Fe58Co14Cr28 alloys. Fe72-xCoxCr28 (10 with a constant Cr content of about 28 at. %, were outside the miscibility gap in the equilibrium phase diagram, and therefore TMT had no effect on the final magnetic properties.
Mohammad Molaahmadi, Majid Tavoosi, Ali Ghasemi, Gholam Reza Gordani,
Volume 20, Issue 2 (6-2023)
Abstract
Investigation the structural and magnetic properties of nanocrystalline Co78Zr17B2Si1W2 alloy during melt spinning and annealing processes were the main goal of this study. In this regard, samples were prepared using vacuum induction melting, melt spinning and subsequent annealing. The specimens were evaluated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Based on results, nanocrystalline Co5Zr single phase with hard magnetic properties (Ms=29.5 emu/g and Hc=2.7 kOe) successfully formed during melt spinning process (at wheel speed of 40 m.s-1). The coercivity value of rapid solidified sample increased to about 3.2 kOe during annealing process up to 400°C. However, more increasing in annealing temperature lead to the transformation of non-equilibrium magnetic Co5Zr phase to stable Zr2Co11 phase, which has distractive effects on final magnetic properties.
Ahmad Ostovari Moghaddam, Olga Zaitseva, Sergey Uporov, Rahele Fereidonnejad, Dmitry Mikhailov, Nataliya Shaburova, Evgeny Trofimov,
Volume 21, Issue 3 (9-2024)
Abstract
High entropy intermetallic compounds (HEICs) are an interesting class of materials combining the properties of multicomponent solid solutions and the ordered superlattices in a single material. In this work, microstructural and magnetic properties of (CoCuFeMnNi)Al, (CoCuFeMnNi)Zn3, (FeCoMnNiCr)3Sn2, (FeCoNiMn)3Sn2 and Cu3(InSnSbGaGe) HEICs fabricated by induction melting are studied. The magnetic properties of the HEICs was determined mainly by the nature of the magnetic momentum of the constituent elements. (CoCuFeMnNi)Al and (CoCuFeMnNi)Zn3 displayed ferromagnetic behavior at 5 K, while indicated linear dependency of magnetization vs. magnetic (i.e. paramagnetic or antiferromagnetic state) at 300 K. The magnetization of (FeCoMnNiCr)3Sn2, (FeCoNiMn)3Sn2 and Cu3(InSnSbGaGe) HEICs at 300 K exhibited a nearly linear dependency to magnetic field. Among all the investigated samples, (CoCuFeMnNi)Al exhibited the best magnetic properties with a saturation magnetization of about Ms = 6.5 emu/g and a coercivity of about Hc = 100 Oe.
