Effect of single-domain particle size and chemical composition on the chain formation in magnetic metal powders

1990 ◽  
Vol 83 (1-3) ◽  
pp. 460-462 ◽  
Author(s):  
I. Dragieva ◽  
D. Buchkov ◽  
M. Slavcheva ◽  
D. Mehandjiev
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Single Domain ◽  
Metal Powders ◽  
Chain Formation ◽  
Single Domain Particle ◽  
Magnetic Metal

scholarly journals Effect of Mechanical Milling on the Magnetic Properties of SrFe12O19

2015 ◽  
Vol 12 (1) ◽  
pp. 28-30
Author(s):  
I Bsoul
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Crystallite Size ◽  
Mechanical Milling ◽  
Single Phase ◽  
Strontium Ferrite ◽  
Single Domain ◽  
Single Domain Particle ◽  
Ferrite Sample

In this work, a single phase strontium ferrite sample was mechanically milled for 60 h. It has been found that the crystallite size reduced by 85%. A dramatic drop (from 4500 to 1600 Oe) in the coercive filed was also observed. The observed reduction in the coercivity was attributed to the reduction of the single domain particle size.

Squareness of NdFeB Stoner-Wohlfarth Hysteresis

2014 ◽  
Vol 802 ◽  
pp. 601-606
Author(s):  
Marcos Flavio de Campos ◽  
Fernanda A.S. da Silva ◽  
José Adilson de Castro
Keyword(s):  
Particle Size ◽  
General Result ◽  
Anisotropy Constant ◽  
Single Domain ◽  
Single Domain Particle ◽  
Hysteresis Curves ◽  
Intrinsic Coercivity ◽  
Grain Diameter

Hysteresis curves were calculated according the Stoner-Wohlfarth (SW) model using values of K2/K1from zero up to 0.25 (where K2is the 2ndorder anisotropy constant and where K1is the 1storder anisotropy constant). The SW calculations assume Nd2Fe14B nanocrystalline magnets with single domain particle size (grain diameter less than 150 nm). The effect of K2on several index of merit of magnets as BHmaxand squareness are discussed. As a general result, increasing K2, the intrinsic coercivity increases. However, the increase of K2almost does not improve the BHmaxof isotropic magnets. It is found that the effect of the K2/K1ratio is coupled with the effect of texture, i.e., the effect of K2is more significant for pronounced texture.

Application of Micromagnetic Models for Barium Ferrite Magnets

2015 ◽  
Vol 820 ◽  
pp. 199-204 ◽  
Author(s):  
Marcos Flavio de Campos ◽  
Fernanda A. Sampaio da Silva
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Coercive Force ◽  
Total Energy ◽  
Barium Ferrite ◽  
Magnetocrystalline Anisotropy ◽  
Single Domain ◽  
Square Root ◽  
Single Domain Particle ◽  
Magnetostatic Energy

The applicability of micromagnetics for phases with high magnetocrystalline anisotropy as barium ferrite Ba2Fe12O19and Nd2Fe14B is discussed. The Stoner-Wohlfarth model is very suitable for such phases, and also for PtFe and PtCo. It was discussed how to take into account the total energy of the system for grain size above the single domain particle size. For this situation of large grain size, the net magnetostatic energy of the system cannot be neglected. From energy considerations, it follows that the coercive force should decrease with the inverse of the square root of the grain size.

Hysteresis Modeling of NdFeB Magnets with High Nd

2016 ◽  
Vol 869 ◽  
pp. 585-590 ◽  
Author(s):  
Marcos Flavio de Campos ◽  
Fernanda A. Sampaio da Silva ◽  
José Adilson de Castro
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Grain Boundaries ◽  
Paramagnetic Phase ◽  
Single Domain ◽  
Hysteresis Model ◽  
Ndfeb Magnets ◽  
Single Domain Particle ◽  
Hysteresis Curves ◽  
Hysteresis Modeling

The Stoner-Wohlfarth hysteresis model can describe very well the hysteresis curves since the assumptions of the model are compatible with the studied samples. These conditions are (i) single domain particle size and (ii) inexistence of interactions between the particles. These conditions are obtained in Nd2Fe14B magnets with nanocrystalline grain size below 200 nm and with high Nd, which promotes a paramagnetic phase at the grain boundaries. In the present study, both isotropic and anisotropic NdFeB magnets are modeled.

scholarly journals Influencing Factors of the Mineral Carbonation Process of Iron Ore Mining Waste in Sequestering Atmospheric Carbon Dioxide

2021 ◽  
Vol 13 (4) ◽  
pp. 1866
Author(s):  
Noor Allesya Alis Ramli ◽  
Faradiella Mohd Kusin ◽  
Verma Loretta M. Molahid
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Chemical Composition ◽  
Iron Ore ◽  
Divalent Cations ◽  
Mining Industry ◽  
Mining Waste ◽  
Aluminum Silicate ◽  
Mineral Carbonation ◽  
Carbonation Process

Mining waste may contain potential minerals that can act as essential feedstock for long-term carbon sequestration through a mineral carbonation process. This study attempts to identify the mineralogical and chemical composition of iron ore mining waste alongside the effects of particle size, temperature, and pH on carbonation efficiency. The samples were found to be alkaline in nature (pH of 6.9–7.5) and contained small-sized particles of clay and silt, thus indicating their suitability for mineral carbonation reactions. Samples were composed of important silicate minerals needed for the formation of carbonates such as wollastonite, anorthite, diopside, perovskite, johannsenite, and magnesium aluminum silicate, and the Fe-bearing mineral magnetite. The presence of Fe2O3 (39.6–62.9%) and CaO (7.2–15.2%) indicated the potential of the waste to sequester carbon dioxide because these oxides are important divalent cations for mineral carbonation. The use of small-sized mine-waste particles enables the enhancement of carbonation efficiency, i.e., particles of <38 µm showed a greater extent of Fe and Ca carbonation efficiency (between 1.6–6.7%) compared to particles of <63 µm (0.9–5.7%) and 75 µm (0.7–6.0%). Increasing the reaction temperature from 80 °C to 150–200 °C resulted in a higher Fe and Ca carbonation efficiency of some samples between 0.9–5.8% and 0.8–4.0%, respectively. The effect of increasing the pH from 8–12 was notably observed in Fe carbonation efficiency of between 0.7–5.9% (pH 12) compared to 0.6–3.3% (pH 8). Ca carbonation efficiency was moderately observed (0.7–5.5%) as with the increasing pH between 8–10. Therefore, it has been evidenced that mineralogical and chemical composition were of great importance for the mineral carbonation process, and that the effects of particle size, pH, and temperature of iron mining waste were influential in determining carbonation efficiency. Findings would be beneficial for sustaining the mining industry while taking into account the issue of waste production in tackling the global carbon emission concerns.

scholarly journals Variation of the Chemical Composition of Waste Cooking Oils upon Bentonite Filtration

Resources ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 108 ◽  
Author(s):  
Alberto Mannu ◽  
Gina Vlahopoulou ◽  
Paolo Urgeghe ◽  
Monica Ferro ◽  
Alessandra Del Caro ◽  
...  
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Solid Phase ◽  
Volatile Fraction ◽  
X Ray Diffraction ◽  
Specific Chemical ◽  
Waste Cooking Oils ◽  
Main Components ◽  
Cooking Oils ◽  
Chemical Groups

The chemical composition and the color of samples of waste cooking oils (WCOs) were determined prior to and after filtration on two different pads of bentonite differing in particle size. The volatile fraction was monitored by headspace solid-phase microextraction (HS-SPME) coupled with gas-chromatography, while the variation of the composition of the main components was analyzed by 1H NMR. Both techniques allowed the detection of some decomposition products, such as polymers, terpenes, and derivatives of the Maillard process. The analysis of the chemical composition prior to and after bentonite treatment revealed a tendency for the clays to retain specific chemical groups (such as carboxylic acids or double bonds), independent of their particle size. A pair comparison test was conducted in order to detect the sensory differences of the intensity of aroma between the WCO treated with the two different bentonites. In addition, characterization of the bentonite by means of powder X-ray diffraction (XRD) and thermogravimetric measurements (TG) was performed.

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