Investigations on the Magnetic Properties of High-Coercivity Nd40Fe30Co15Al10B5 Bulk Amorphous Alloys

2005 ◽  
Vol 877 ◽  
Author(s):  
L. Bessais ◽  
C. Djëga-Mariadassou ◽  
N. X. Phuc
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Magnetic Behavior ◽  
High Energy ◽  
High Coercivity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Leading Role ◽  
Remanence Ratio ◽  
Transmission Electron

AbstractNd40Fe30Co15Al10B5 bulk amorphous prepared by high energy milling shows a coercivity of 8.1 kOe with a Curie temperature of 645 K. The controlled nanocrystallization enhances the coercivity to 20 kOe and the remanence ratio is equal to 0.59. The coexistence of two crystalline magnetic phases, ferromagnetic Nd2(Fe,Co,Al)14B and antiferromagnetic Nd6(Fe,Co,Al)14 are revealed by x-ray diffraction, high-resolution transmission electron microscopy, magnetization measurements, and Mössbauer spectrometry. The grain size for optimal magnetic properties is around 30 nm. The nucleation process may play a leading role in the high magnetic behavior.

Effect of Nitridation Magnetic Properties of Nanocrystalline Fe-Co Alloy Powders

2010 ◽  
Vol 654-656 ◽  
pp. 1106-1109
Author(s):  
Ya Qiong He ◽  
Chang Hui Mao ◽  
Jian Yang
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Alloy Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Transmission Electron ◽  
Nitridation Temperature ◽  
Microstructure And Magnetic Properties

Nanocrystalline Fe-Co alloy powders, which were prepared by high-energy mechanical milling, were nitrided under the mixing gas of NH3/H2 in the temperature range from 380°C to 510°C. X-ray diffraction (XRD) was used to analyze the grain size and reaction during the processing. The magnetic properties of the nitrided powders were measured by Vibrating Sample Magnetometer (VSM). The results show that with the appearance of Fe4N phase after nitride treatment, and the grain-size of FeCo phase decreases with the increase of nitridation temperature between 380°C to 450°C.The saturation magnetization of nitrided alloy powder treated at 480°C is about 18% higher than that of the initial Fe-Co alloy powder, accompanied by the reduction of the coercivity. Transmission electron microscope (TEM) was used, attempting to further analyze the effect of Fe4N phase on microstructure and magnetic properties of the powder mixtures.

Influence of Alloying Additions on Enhancement of Soft Magnetic Properties Effect and Crystallization in FeXSiB (X=Cu, V, Co, Zr, Nb) Amorphous Alloys

2007 ◽  
Vol 130 ◽  
pp. 171-174 ◽  
Author(s):  
Z. Stokłosa ◽  
G. Badura ◽  
P. Kwapuliński ◽  
Józef Rasek ◽  
G. Haneczok ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Crystallization Process ◽  
Annealing Temperature ◽  
Magnetic Measurements ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
X Ray ◽  
Second Stage ◽  
Transmission Electron

The crystallization and optimization of magnetic properties effects in FeXSiB (X=Cu, V, Co, Zr, Nb) amorphous alloys were studied by applying X-ray diffraction methods, high resolution transmission electron microscopy (HRTEM), resistometric and magnetic measurements. The temperatures of the first and the second stage of crystallization, the 1h optimization annealing temperature and the Curie temperature were determined for different amorphous alloys. Activation energies of crystallization process were obtained by applying the Kissinger method. The influence of alloy additions on optimization effect and crystallization processes was carefully examined.

scholarly journals Size Effect on the Structural and Magnetic Properties of Nanosized PerovskiteLaFeO3Prepared by Different Methods

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Nguyen Thi Thuy ◽  
Dang Le Minh
Keyword(s):  
Magnetic Properties ◽  
Electron Microscope ◽  
Room Temperature ◽  
High Energy ◽  
Ferromagnetic Behavior ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation

Nanosized LaFeO3material was prepared by 3 methods: high energy milling, citrate gel, and coprecipitation. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) show that the orthorhombic LaFeO3phase was well formed at a low sintering temperature of 500°C in the citrate-gel and co-precipitation methods. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations indicate that the particle size of the LaFeO3powder varies from 10 nm to 50 nm depending on the preparation method. The magnetic properties through magnetization versus temperatureM(T)and magnetization verses magnetic fieldM(H)characteristics show that the nano-LaFeO3exhibits a weak ferromagnetic behavior in the room temperature, and theM(H)curves are well fitted by Langevin functions.

Local Structure and Magnetic Properties of FeMnAl Nanocrystalline and Amorphous Alloys

2011 ◽  
Vol 277 ◽  
pp. 100-105
Author(s):  
Kontan Tarigan ◽  
D. S. Yang ◽  
S. C. Yu
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Milling Time ◽  
Magnetic Behavior ◽  
Time Varying ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystalline And Amorphous ◽  
Magnetization Saturation ◽  
X Ray Absorption

The structural and the magnetic properties of nanocrystalline and amorphous Fe55Mn10Al35 alloys prepared by the mechanical alloying process are studied as functions of the milling time varying from 1 hr to 48 hrs. Structural analyses based on X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) reveal that the alloying process took place after 12-hr milling. Nanocrystalline alloys are found until 24-hrs milling, and an amorphous phase afterward. Concerning the magnetic behavior, the data obtained from a vibrating sample magnetometer show that both the magnetization saturation (Ms) and the coercivity (Hc) are dependent strongly on the milling time and the crystallite size. By adjusting the milling time, both appropriate structural transformation and magnetization values are obtained.

scholarly journals Nanocomposite of CeO2 and High-Coercivity Magnetic Carrier with Large Specific Surface Area

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
Alice Reznickova Mantlikova ◽  
Jiri Plocek ◽  
Barbara Pacakova ◽  
Simona Kubickova ◽  
Ondrej Vik ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Synthesis Method ◽  
High Specific Surface Area ◽  
High Coercivity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

We succeeded in the preparation of CoFe2O4/CeO2 nanocomposites with very high specific surface area (up to 264 g/m2). First, highly crystalline nanoparticles (NPs) of CoFe2O4 (4.7 nm) were prepared by hydrothermal method in water-alcohol-oleic acid system. The oleate surface coating was subsequently modified by ligand exchange to citrate. Then the NPs were embedded in CeO2 using heterogeneous precipitation from diluted Ce3+ sulphate solution. Dried samples were characterized by Powder X-Ray Diffraction, Energy Dispersive X-Ray Analysis, Scanning and Transmission Electron Microscopy, Mössbauer Spectroscopy, and Brunauer-Emmett-Teller method. Moreover, detailed investigation of magnetic properties of the bare NPs and final composite was carried out. We observed homogeneous embedding of the magnetic NPs into the CeO2 without significant change of their size and magnetic properties. We have thus demonstrated that the proposed synthesis method is suitable for preparation of extremely fine CeO2 nanopowders and their nanocomposites with NPs. The morphology and magnetic nature of the obtained nanocomposites make them a promising candidate for magnetoresponsive catalysis.

scholarly journals Multiscale Copper-µDiamond Nanostructured Composites

2012 ◽  
Vol 730-732 ◽  
pp. 925-930
Author(s):  
Daniela Nunes ◽  
Vanessa Livramento ◽  
Horácio Fernandes ◽  
Carlos Silva ◽  
Nobumitsu Shohoji ◽  
...  
Keyword(s):  
Pure Copper ◽  
Thermal Stabilization ◽  
Hot Extrusion ◽  
Processing Parameters ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optimal Processing ◽  
Novel Approach ◽  
Transmission Electron

Nanostructured copper-diamond composites can be tailored for thermal management applications at high temperature. A novel approach based on multiscale diamond dispersions is proposed for the production of this type of materials: a Cu-nDiamond composite produced by high-energy milling is used as a nanostructured matrix for further dispersion of micrometer sized diamond. The former offers strength and microstructural thermal stability while the latter provides high thermal conductivity. A series of Cu-nDiamond mixtures have been milled to define the minimum nanodiamond fraction suitable for matrix refinement and thermal stabilization. A refined matrix with homogenously dispersed nanoparticles could be obtained with 4 at.% nanodiamond for posterior mixture with mDiamond and subsequent consolidation. In order to define optimal processing parameters, consolidation by hot extrusion has been carried out for a Cu-nDiamond composite and, in parallel, for a mixture of pure copper and mDiamond. The materials produced were characterized by X-ray diffraction, scanning and transmission electron microscopy and microhardness measurements.

Structural changes in titanium dioxide nanocrystals during plastic deformation

2005 ◽  
Vol 38 (5) ◽  
pp. 749-756 ◽  
Author(s):  
Ulrich Gesenhues
Keyword(s):  
Structural Changes ◽  
Crystal Size ◽  
Lower Layer ◽  
High Energy ◽  
Primary Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hall Method ◽  
Means Of Transmission

The polygonization of 200 nm rutile crystals during dry ball-milling at 10gwas monitored in detail by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM results showed how to modify the Williamson–Hall method for a successful evaluation of crystal size and microstrain from XRD profiles. Macrostrain development was determined from the minute shift of the most intense reflection. In addition, changes in pycnometrical density were monitored. Accordingly, the primary crystal is disintegrated during milling into a mosaic of 12–35 nm pieces where the grain boundaries induce up to 1.2% microstrain in a lower layer of 6 nm thickness. Macrostrain in the interior of the crystals rises to 0.03%. The pycnometrical density, reflecting the packing density of atoms in the grain boundary, decreases steadily by 1.1%. The results bear relevance to our understanding of plastic flow and the mechanism of phase transitions of metal oxides during high-energy milling.

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

Nickel Ferrite: Combustion Synthesis, Characterization and Magnetic Properties

2005 ◽  
Vol 498-499 ◽  
pp. 618-623 ◽  
Author(s):  
Ana Cristina Figueiredo de Melo Costa ◽  
Lucianna Gama ◽  
M.R. Morelli ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Magnetic Properties ◽  
Nickel Ferrite ◽  
High Speed ◽  
High Specific Surface Area ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Railway Systems ◽  
Transmission Electron ◽  
Dry Pressing

Nanosized spinel nickel ferrite particles have attracted considerable attention and efforts continue to investigate them for their technological importance to the microwave industries, high speed digital tap or disk recording, repulsive suspension for use in levitated railway systems, ferrofluids, catalysis and magnetic refrigeration systems. Nanosize nickel ferrite powders (NiFe2O4) have been prepared by combustion reaction using nitrates and urea as fuel. The resulting powders were characterized by X-ray diffraction (XRD), BET, and transmission electron microscopy (TEM). The results showed nanosize nickel ferrite powders with high specific surface area (55.21 m2/g). The powders showed extensive XRD line broadening and the crystallite size calculated from the XRD line broadening was 18.0 nm. The samples were uniaxially compacted by dry pressing, sintered at 1200°C/2h and characterized by bulk density, SEM and magnetic properties measurements. The samples showed uniform microstructures with grain size of 4.45 μm, maximum flux density of 0.18T, field coercive of the 488 A/m, and hysteresis loss of 47.58 W/kg.

Epitaxial growth of BaO and SrO with new crystal structures using mass-separated low-energy O+ beams

1993 ◽  
Vol 8 (2) ◽  
pp. 321-323 ◽  
Author(s):  
Ryusuke Kita ◽  
Takashi Hase ◽  
Hiromi Takahashi ◽  
Kenichi Kawaguchi ◽  
Tadataka Morishita
Keyword(s):  
Lattice Constant ◽  
High Energy ◽  
Low Energy ◽  
Diffraction Reflection ◽  
High Energy Electron ◽  
Bulk Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Cubic Structure

The growth of BaO and SrO on SrTiO3(100) substrates using mass-separated low-energy (50 eV) O+ beams has been studied using x-ray diffraction, reflection high-energy electron diffraction, and high-resolution transmission electron microscopy. It was found that the BaO and SrO films have been epitaxially grown with new structures different from those of corresponding bulk crystals: The BaO films have a cubic structure with a lattice constant of 4.0 Å, and the SrO films have a tetragonal structure with a lattice constant of a = 3.7 Å parallel to the substrate and with c = 4.0 Å normal to the substrate.

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