Structure and Magnetic Properties of Strontium Hexaferrite Nanopowders Prepared by Mechanochemical Synthesis

2006 ◽  
Vol 45 ◽  
pp. 321-326 ◽  
Author(s):  
Cornel Miclea ◽  
Constantin Tanasoiu ◽  
Corneliu Florin Miclea ◽  
I. Spanulescu ◽  
Anca Gheorghiu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Mechanochemical Synthesis ◽  
Milled Powder ◽  
Magnetic Behavior ◽  
High Energy ◽  
Strontium Hexaferrite ◽  
Synthesis Process ◽  
Energy Product ◽  
Suitable Heat Treatment ◽  
Structural Deformations

Strontium hexaferrite nanopowders were prepared by mechanochemical synthesis from strontium and iron oxides using a high energy ball mill after 50 hours of milling. The synthesis process was checked by X-Ray diffractograms on powders milled for different times. The magnetic properties of hexaferrite nanopowder, both compacted and dispersed in a nonmagnetic matrix were determined. Severe stresses and structural deformations were introduced by mechanical processing, but they were eliminated, to a great extent, by a suitable heat treatment of the milled powder at 1000 oC for one and a half hour. Coercivities as high as 6600 Oe and specific magnetization of 65 emu/g were found for annealed noninteracting nanopowders. Such values are very near to the theoretical values for strontium ferrite. The magnetic behavior of such powders can be rather well described by the coherent rotation model of Stoner-Wohlfarth for an assembly of single domain particles oriented at random. Sintered bodies of such powders produced magnets with a high HC of 4600 Oe, a Br of 2100 Gs and an energy product maxim of approximately 1.85 MGOe.

scholarly journals Microstructural and Magnetic Behavior of Nanocrystalline Fe-12Ni-16B-2Si Alloy Synthesis and Characterization

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1679
Author(s):  
Kaouther Zaara ◽  
Mohamed Khitouni ◽  
Lluisa Escoda ◽  
Joan Saurina ◽  
Joan-Josep Suñol ◽  
...  
Keyword(s):  
Solid Solution ◽  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Milling Time ◽  
Milled Powder ◽  
Magnetic Behavior ◽  
Phase Evolution ◽  
High Energy ◽  
Refined Microstructure ◽  
Hard Magnetic Properties

The nanocrystalline Fe70Ni12B16Si2 (at.%) alloy was prepared by mechanical alloying (MA) of elemental powders in a high-energy planetary ball mill. Phase evolution, microstructure, thermal behavior and magnetic properties were investigated. It was found that a body-centered cubic structured solid solution started to form after 25 h milling and a faced-centered cubic structure solid solution started to form after 50 h of milling; its amount increased gradually with increasing milling time. The BCC and the FCC phases coexisted after 150 h of milling, with a refined microstructure of 13 nm and a 10 nm crystallite size. The as-milled powder was annealed at 450 °C and 650 °C and then investigated by vibrating sample magnetometry (VSM). It was shown that the semi-hard magnetic properties are affected by the phase transformation on annealing. The saturation magnetization decreases after annealing at 450 °C, whereas annealing at 650 °C improves the magnetic properties of 150 h milled powders through the reduction of coercivity from 109 Oe to 70 Oe and the increase in saturation magnetization.

Synthesis and Magnetic Properties of SrFe12-XCoxO19 (x= 0- 2) Hexaferrite Nanoparticles

2012 ◽  
Vol 622-623 ◽  
pp. 925-929 ◽  
Author(s):  
M. Zargar Shoushtari ◽  
S E. Mousavi Ghahfarokhi ◽  
F. Ranjbar
Keyword(s):  
Magnetic Properties ◽  
Magnetic Measurements ◽  
Sol Gel ◽  
Anisotropy Field ◽  
Strontium Hexaferrite ◽  
Nominal Composition ◽  
Second Phase ◽  
Energy Product ◽  
Crystalline Anisotropy ◽  
Magnetic Remanence

In this paper, a batch of M- type strontium hexaferrite samples with nominal composition of SrFe12-xCoxO19(where x= 0- 2), have been synthesized via sol- gel method. In the synthesis of samples, first a precursor gel was prepared, and then dry- gel was calcined at 1000°C for 2 hours to obtain the nano- SrFe12-xCoxO19. The XRD results revealed that for SrFe12-xCoxO19 samples with x≤0.5, all of them have single- phase hexaferrite structure and also this data suggests that the F 3+ ions are substituted by Co2+ ions in the crystallography sites of the SrFe12-xCoxO19, but for the samples with x>0.5, the second phase of CoFe2O4 is appeared and suggests that the Co2+ ions also make a distinct phase in the samples. The magnetic properties, such as saturation magnetization (Ms), magnetic remanence (Mr), magnetic coercivity (Hc), squareness ratio (Mr/Ms), crystalline anisotropy field (Ha), energy product [(BH)max] and the susceptibility χ as the derivative of M with respect to H of the upper branch of the hysteresis loop were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). The magnetic measurements revealed that the coercively (Hc) values of all the samples decrease with increasing dopant contents.

AN INVESTIGATION INTO MECHANOCHEMICAL SYNTHESIS OF NANOCRYSTALLINE HEXAFERRITE POWDER

2011 ◽  
Vol 25 (07) ◽  
pp. 987-993
Author(s):  
S. SADEGHI-NIARAKI ◽  
S. A. SEYYED EBRAHIMI ◽  
SH. RAYGAN
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Milled Powder ◽  
Particle Morphology ◽  
Average Crystallite Size ◽  
Phase Evolution ◽  
High Energy ◽  
Strontium Hexaferrite ◽  
Electron Microscopes

Nanocrystalline strontium hexaferrite powder has been prepared by a new mechanochemical method in which the single phase hexaferrite was obtained via a sol–gel autocombustion process followed by an intermediate high energy milling step and subsequent annealing. The effects of the intermediate milling on the phase evolution, crystallite size and annealing behavior of the final products were investigated using the X-ray diffraction (XRD) technique. The single phase strontium hexaferrite was obtained at an annealing temperature of 800°C, while this temperature was 1,000°C for the powder synthesized without milling. It could be seen that an intermediate milling accelerates the formation of strontium hexaferrite during the calcination process. The results showed that in the milled powder, the average crystallite size of the ferrite was about 40 nm and much smaller than that of the nonmilled powder. Magnetic properties were also measured by a vibrating sample magnetometer (VSM). The particle morphology was then studied by scanning and transmission electron microscopes (SEM and TEM).

Adjacent Layer Composition Effects on Fetbco Thin Film Magnetic Properties

1995 ◽  
Vol 384 ◽  
Author(s):  
Michael B. Hintz
Keyword(s):  
Magnetic Properties ◽  
Ion Beam ◽  
Magnetic Layer ◽  
Magnetic Behavior ◽  
Relative Magnitude ◽  
Adjacent Layer ◽  
Energy Product ◽  
Magnetic Layers ◽  
20 Nm ◽  
Layer Composition

ABSTRACTThe magneto-optical (MO) layer in current rare earth-transition metal (RE-TM) based MO recording media is typically 20 nm to 60 nm thick. It has been suggested, however, that media structures employing a multiplicity of thinner MO layers may be advantageous, e.g., for multilevel recording applications [1] or media noise reduction [2]. As magnetic layer thickness is reduced, interactions among magnetic layers and adjacent materials can have an increasingly large influence on magnetic properties; in many instances, these interactions can dominate the observed magnetic behavior.As a means of studying MO layer - adjacent layer interactions, we have used thin (≈3 nm) films of several materials to separate single 24 nm thick ion-beam-deposited FeTbCo layers into N thinner layers of 24/N nm thickness (N × 24/N). As N increases, the FeThCo magnetic properties generally change; however, the relative magnitude of the changes is strongly dependent upon the adjacent layer composition. Magnetization (Ms), energy product (MsHc) at 30 C and Curie temperature data for 1 × 24 nm structures and 6 × 4 nm structures are compared and discussed for specimens employing SiCx, Six, YOx, HfOx, Si and SiOx adjacent layer materials.

Mössbauer and magnetization studies of mechanically milled nanocrystalline Fe1–xAlx alloys

2015 ◽  
Vol 93 (11) ◽  
pp. 1257-1263
Author(s):  
S. Rajan ◽  
R. Shukla ◽  
A. Kumar ◽  
A. Vyas ◽  
S. Khan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Behavior ◽  
High Energy ◽  
Milling Process ◽  
Transmission Electron ◽  
Bulk Magnetization ◽  
Hyperfine Field Distributions ◽  
Equilibrium Process ◽  
Energy Ball ◽  
Evolution Of Microstructure

Changes in the magnetic behavior of Fe1–xAlx (x = 0.3, 0.4, 0.5, 0.6) powders during mechanical alloying have been studied. The ball milling process leads to formation of solid state reaction assisted by severe plastic deformation because of which crystallite size is reduced and as a result of which interesting magnetic properties are developed. The evolution of magnetic order in high-energy ball-milled Fe–Al solid solution is investigated using 57Fe Mössbauer spectroscopy and vibrating sample magnetometer. Mössbauer spectra and the hyperfine field distributions of all the samples show the presence of both magnetic and paramagnetic components in the samples. The corresponding bulk magnetization studies also show that the Al rich samples are also ferromagnetic, which can be attributed to the presence of disordered Fe-rich phases due to the non-equilibrium process of alloying. In Fe-rich samples, the formation of an off stoichiometric Fe3Al phase is favored while in the case of Al-rich samples both Al-rich phases and clustering of Fe and Al atoms are present. The systematic variation in the magnetic properties has been qualitatively correlated with the evolution of microstructure, reduction in grain size (obtained using transmission electron microscopy) and enhanced intergranular exchange coupling.

Magnetic Properties of Nanocrystalline Fe50Co50 Powders

2003 ◽  
Vol 788 ◽  
Author(s):  
Shashishekar Basavaraju ◽  
Ian Baker
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Magnetic Force ◽  
Milling Time ◽  
Magnetic Behavior ◽  
High Energy ◽  
Soft Magnetic ◽  
Scanning Calorimetry ◽  
High Energy Ball Mill ◽  
Energy Ball

ABSTRACTNanocrystalline stoichiometric FeCo powders were prepared by mechanically alloying elemental Fe and Co powders using a high-energy ball mill. The microstructural evolution was studied as a function of milling time and subsequent annealing using X-ray diffractometry and differential scanning calorimetry. The magnetic behavior of the specimens was characterized using a vibrating sample magnetometer and a magnetic force microscope. A reduction in grain size coupled with an increase in coercivity was observed as function of milling time. The smallest grain size of 4 nm, which exhibited a coercivity of 122 Oe and magnetization of 2 T at room temperature, was obtained after 240 h of milling. The reduction in grain size during milling was not accompanied by enhanced soft magnetic properties.

scholarly journals Preparation of strontium hexaferrite magnets from celestite and blue dust by mechanochemical route

2008 ◽  
Vol 44 (1) ◽  
pp. 91-100 ◽  
Author(s):  
R.K. Tiwary ◽  
S.P. Narayan ◽  
O.P. Pandey
Keyword(s):  
Iron Ore ◽  
Single Phase ◽  
High Energy ◽  
Strontium Hexaferrite ◽  
Ferrite Powder ◽  
Sintered Magnet ◽  
X Ray ◽  
Energy Product ◽  
Long Time ◽  
Iron Ore Fines

In the present investigation celestite (natural ore of strontium) and blue dust (iron ore fines) have been used for the preparation of strontium hexaferrite powder. The mechanical alloying process has been adopted to prepare strontium hexaferrite powder. The celestite after chemical upradation and physically upgraded blue dust alongwith sodium carbonate was taken for the preparation of strontium hexaferrite in this experiment. The high-energy planetary ball mill with tungsten carbide jar and ball was used to prepare strontium hexaferrite powder. A long time of ball milling for different duration has led to displacement solid-state reaction. At the end of each experiment the product was washed thoroughly and dried. The X-ray diffaction study after annealing shows the development of single-phase strontium hexaferrite after 40 hrs. of milling. The resultant powder was compacted under magnetic field and sintered to prepare the magnet after annealing the ferrite powder. The magnetic properties were measured by Pulse magneto meter. The moderate value of coercivity, remanence and energy product were observed in this sintered magnet. The work illustrates the feasibility to prepare strontium hexaferrite magnetic powders directly from natural ores which can reduce the total cost of production as compared to conventional method.

Investigation on the Improvement of Magnetic Properties by Hot Deformation Processes for NdFeB Magnets

2014 ◽  
Vol 626 ◽  
pp. 317-322 ◽  
Author(s):  
Yen Ju Chen ◽  
Chao Cheng Chang ◽  
Po Jen Hsiao ◽  
Can Xun Chang
Keyword(s):  
Plastic Deformation ◽  
Magnetic Properties ◽  
Strain Rate ◽  
Process Parameters ◽  
Effective Strain ◽  
High Energy ◽  
Experimental Results ◽  
Ndfeb Magnets ◽  
Energy Product ◽  
Key Factor

Traditionally, NdFeB magnets with high remanent flux density or high energy product could only be manufactured through altering the material compounds. In recent years, studies indicated that the magnet properties of NdFeB magnets could be improved through plastic deformation. These studies pointed out that the degree of plastic deformation is a key factor to improve magnetic properties. However, there are still many other process parameters that could affect the magnetic properties either positively or negatively. In this paper, process parameters such as strain, strain rate, and temperature are studied to illustrate their influences on the magnetic properties of NdFeB magnets. The magnetic property could be greatly improved when the preferred orientation appears on the microstructure of deformed NdFeB magnets. One of the experimental results showed that the energy product value had been increased by 76.7% when the effective strain value had reached 0.65. Experimental results also showed that strain rate is a dominating factor with regard to the flow stress of material. Through a proper combination of these parameters, one can obtain NdFeB magnets with their magnetic properties greatly improved.

SYNTHESIS OF NANO CRYSTALLINE BARIUM HEXAFERRITE IN THE PRESENCE OF SALT CATALYSTS

2008 ◽  
Vol 22 (18n19) ◽  
pp. 3120-3126
Author(s):  
ATEFEH HASSANIRAD ◽  
A. ATAIE ◽  
R. NIKKHAH-MOSHAEE
Keyword(s):  
Milled Powder ◽  
Barium Hexaferrite ◽  
High Energy ◽  
Synthesis Process ◽  
Oxide Ceramic ◽  
Nano Crystalline ◽  
High Energy Ball Mill ◽  
Powder Particles ◽  
Xrd Patterns ◽  
20 Nm

Nano crystalline barium hexaferrite, BaFe 12 O 19, were synthesized from mixture of barium acetate and iron oxide by conventional mixed oxide ceramic method. The mixture of precursors together with a 3wt% salt-catalyst (ammonium and sodium chlorides) was intensively milled by high energy ball mill for 10 hr. The influence of addition of catalyst on the synthesis process has been studied by XRD, SEM, DTA/TG and TEM techniques. Analysis of the XRD patterns indicates that salt-catalysts can strongly alter the morphology and phase composition of ball milled powder particles. Sample with 3wt% NH 4 Cl after milling for 10 hr and annealing at 900°C for 1 hr exhibited single phase barium hexaferrite with mean crystallite size of 20 nm.

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