Microwave Properties of Polymer Composites Containing Combinations of Micro- and Nano-Sized Magnetic Fillers

2008 ◽  
Vol 8 (2) ◽  
pp. 650-654 ◽  
Author(s):  
Svetoslav Kolev ◽  
Tatyana Koutzarova ◽  
Andrey Yanev ◽  
Chavdar Ghelev ◽  
Ivan Nedkov
Keyword(s):  
Magnetic Material ◽  
Magnetocrystalline Anisotropy ◽  
Average Particle Size ◽  
Anisotropy Field ◽  
Anisotropy Constant ◽  
Strontium Hexaferrite ◽  
Filler Concentration ◽  
Average Particle ◽  
Effective Anisotropy ◽  
Magnetite Particles

We investigated the microwave absorbing properties of composite bulk samples with nanostructured and micron-sized fillers. As magnetic fillers we used magnetite powder (Fe3O4 with low magnetocrystalline anisotropy) and strontium hexaferrite (SrFe12O19 with high magnetocrystalline anisotropy). The dielectric matrix consisted of silicone rubber. The average particle size was 30 nm for the magnetite powder and 6 μm for the strontium hexaferrite powder. The micron-sized SrFe12O19 powder was prepared using a solid-state reaction. We investigated the influence of the filler concentration and the filler ratio (Fe3O4/SrFe12O19) in the polymer matrix on the microwave absorption in a large frequency range (1 ÷ 18 GHz). The results obtained showed that the highly anisotropic particles become centers of clusterification and the small magnetite particles form magnetic balls with different diameter depending on the concentration. The effect of adding micron-sized SrFe12O19 to the nanosized Fe3O4 filler in composites absorbing structures has to do with the ferromagnetic resonance (FMR) shifting to the higher frequencies due to the changes in the ferrite filler's properties induced by the presence of a magnetic material with high magnetocrystalline anisotropy. The two-component filler possesses new values of the saturation magnetization and of the anisotropy constant, differing from those of both SrFe12O19 and Fe3O4, which leads to a rise in the effective anisotropy field. The results demonstrate the possibility to vary the composite's absorption characteristics in a controlled manner by way of introducing a second magnetic material.

A New Method for Direct Determination of the Recoilless Fraction with Application to Magnetic Nanoparticles

2002 ◽  
Vol 721 ◽  
Author(s):  
Monica Sorescu
Keyword(s):  
Room Temperature ◽  
Average Particle Size ◽  
Direct Determination ◽  
Average Particle ◽  
Lattice Method ◽  
Recoilless Fraction ◽  
Single Room ◽  
Magnetite Particles ◽  
Physical Mixtures

AbstractWe propose a two-lattice method for direct determination of the recoilless fraction using a single room-temperature transmission Mössbauer measurement. The method is first demonstrated for the case of iron and metallic glass two-foil system and is next generalized for the case of physical mixtures of two powders. We further apply this method to determine the recoilless fraction of hematite and magnetite particles. Finally, we provide direct measurement of the recoilless fraction in nanohematite and nanomagnetite with an average particle size of 19 nm.

scholarly journals Effect of the polymeric coating over Fe3O4 particles used for magnetic separation

2010 ◽  
Vol 8 (5) ◽  
pp. 1041-1046 ◽  
Author(s):  
Raúl Reza ◽  
Carlos Martínez Pérez ◽  
Claudia Rodríguez González ◽  
Humberto Romero ◽  
Perla García Casillas
Keyword(s):  
Particle Size ◽  
Magnetite Nanoparticles ◽  
Average Particle Size ◽  
Spherical Shape ◽  
Polymeric Coating ◽  
Average Particle ◽  
Synthesis Conditions ◽  
Aging Conditions ◽  
Magnetite Particles ◽  
Average Size

AbstractIn this work, the synthesis of magnetite nanoparticles by two variant chemical coprecipitation methods that involve reflux and aging conditions was investigated. The influence of the synthesis conditions on particle size, morphology, magnetic properties and protein adsorption were studied. The synthesized magnetite nanoparticles showed a spherical shape with an average particle size directly influenced by the synthesis technique. Particles of average size 27 nm and 200 nm were obtained. When the coprecipitation method was used without reflux and aging, the smallest particles were obtained. Magnetite nanoparticles obtained from both methods exhibited a superparamagnetic behavior and their saturation magnetization was particle size dependent. Values of 67 and 78 emu g−1 were obtained for the 27 nm and 200 nm magnetite particles, respectively. The nanoparticles were coated with silica, aminosilane, and silica-aminosilane shell. The influence of the coating on protein absorption was studied using Bovine Serum Albumin (BSA) protein.

Kinetics of Structural Changes in Strontium Hexa-Ferrite Powder during Milling in Beater Mill

2020 ◽  
Vol 989 ◽  
pp. 199-203
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov ◽  
Viktor P. Kryzhanovsky
Keyword(s):  
Particle Size ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Milling Process ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Relative Deformation ◽  
Ferrite Powder ◽  
Electromagnetic Effect

The paper presents the results of experimental studies of strontium hexa-ferrite average particle size and structural characteristics changes during milling process. Coarse strontium hexaferrite was milled in beater mill, without and with electromagnetic effect. Electromagnetic effect was produced by constant and alternating gradient magnetic fields with mutually perpendicular induction lines. Particle sizes were measured by microscopic methods, and structural characteristics were calculated by processing of X-ray diffractograms. Diffraction studies showed that during milling process, both with and without electromagnetic effect, the most intensive changes of coherent scattering region (CSR) sizes, dislocation densities and relative deformation of particulate material occur at earlier stage of milling. At this stage the speed of average particle size decrease is maximal. At later stage both average particle size and structural characteristic changes correlate and have asymptotic character.

scholarly journals STUDYING MORPHOLOGY OF SUSPENSIONS BY THE METHOD OPTICAL SPECTROSCOPY

2020 ◽  
pp. 54-62
Author(s):  
Алена Игорьевна Маркова ◽  
Максим Вадимович Ярусов ◽  
Светлана Дмитриевна Хижняк ◽  
Павел Михайлович Пахомов
Keyword(s):  
Optical Spectroscopy ◽  
Spectroscopic Method ◽  
Average Particle Size ◽  
Filler Concentration ◽  
Average Particle ◽  
Uv Visible ◽  
Microscopy Data ◽  
Average Size ◽  
Radiation Passing ◽  
Good Agreement

Методом оптической спектроскопии (УФ, видимая и ИК области спектра) исследованы две суспензии: вазелиновое масло (ВМ) наполненное слюдой и BaSO различной концентрации. Разработанный метод основан на анализе рассеивающей компоненты электромагнитного излучения, проходящего через образец, позволяющий определить средний размер и распределение рассеивающих частиц по размерам. Установлено, что с увеличением концентрации наполнителя частицы агрегируют, вследствие чего средний размер частиц увеличивается. Результаты, полученные спектроскопическим методом, хорошо согласуются с данными оптической микроскопии. Two suspensions were studied by optical spectroscopy (UV, visible, and IR): vaseline oil (VM) filled with mica and BaSO of different concentrations. The developed method is based on the analysis of the scattering component of electromagnetic radiation passing through the sample, which makes it possible to determine the average size and size distribution of scattering particles. It was found that with increasing filler concentration, the particles aggregate, resulting in an increase in the average particle size. The results obtained by the spectroscopic method are in good agreement with the optical microscopy data.

The Influence of Milling Regimes in Beater Mill on Particle Size Distribution and Structural Characteristics of Strontium Hexaferrite Powder

2018 ◽  
Vol 284 ◽  
pp. 158-162
Author(s):  
I.N. Yegorov ◽  
Nikolay Ya. Egorov
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Structural Parameters ◽  
Average Particle Size ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Electromagnetic Effect ◽  
Coarse Material

The paper experimentally substantiates effectiveness of method of milling particulate ferromagnetic materials in magneto fluidized bed. Comparative results of particle size distributions and structural parameters of strontium hexaferrite SrFe12O19 powder obtained by milling coarse material in beater mill without electromagnetic effect and in same mill with formation of magneto fluidized bed from mill material are presented. The magneto fluidized bed is formed by constant and alternating gradient magnetic fields with induction lines that are mutually perpendicular and parallel to the plane of rotating beaters. It is shown that application of electromagnetic effect to milling coarse material in beater mill allowed to greatly intensify that process, significantly increase powder quality: increase particle size distribution uniformity and decrease average particle size from 1558.50 μm to 0.56 μm after 120 minutes of processing in the mill. X-ray diffraction analysis showed that milling in beater mill in magneto fluidized bed leads to reduction of coherent-scattering region size, increase of lattice microstrain and dislocation density, making powder more active during sintering process.

scholarly journals Influence of electromagnetic effect parameters on ferromagnetic powders fluidity

2018 ◽  
Vol 226 ◽  
pp. 03002
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov
Keyword(s):  
Symmetry Axis ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Barium Hexaferrite ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Particle Sizes ◽  
Electromagnetic Effect ◽  
Flow Through ◽  
Particulate Medium

The paper presents result of experimental studies of ferromagnetic powders fluidity management by effecting on particulate medium with constant and alternating gradient magnetic fields. Induction lines of constant magnetic field are perpendicular to symmetry axis of powder hopper. Alternating field is created by electromagnet with one tapering pole and has higher induction gradient values near hopper outlet. These fields form magneto fluidized bed from powder in hopper allowing powders of barium and strontium hexaferrite to flow through the hopper outlet. Dependencies of efflux speed from parameters of electromagnetic fields are presented for barium hexaferrite powder with average particle size 1 μm and strontium hexaferrite powders with average particle sizes 1 and 9 μm.

Milling Duration Influence on Strontium Hexaferrite Technological Characteristics

2021 ◽  
Vol 410 ◽  
pp. 730-734
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov ◽  
Svetlana I. Egorova
Keyword(s):  
Particle Size ◽  
Powder Metallurgy ◽  
Bulk Density ◽  
Fluidized Bed ◽  
Average Particle Size ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Actual Problem ◽  
Technological Characteristics ◽  
Milling Duration

Fine powders of strontium hexaferrite are widely used in powder metallurgy for the production of permanent magnets resistant to atmospheric oxygen and high working temperatures. Obtaining powders with predefined technological characteristics in minimal time and with minimal energy consumption is an actual problem of powder metallurgy. The paper provides the results of experimental studies of technological characteristics of strontium hexaferrite powder (SrFe12O19) during milling in a beater mill. Mechanical milling of coarse strontium hexaferrite was carried out in the mill with the system of rotating beaters for 120 minutes without and with the creation of a pseudo fluidized bed. The fluidization was formed by a perpendicular constant and alternating magnetic field with induction gradients of 150 and 210 mT/m. Average particle size and powder bulk density dependencies from milling time were studied. Experimental data show that milling with the formation of a magneto fluidized bed allows intensifying the process. Beginning from 70 minutes, the dependencies of average particle size and bulk density come to almost asymptotic behavior making further milling rather ineffective. Carried out research allows choosing optimal milling duration for obtaining the required average particle size.

scholarly journals Temperature Dependence of Anisotropy in Ti and Gd Doped NiMnGa-Based Multifunctional Ferromagnetic Shape Memory Alloys

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2906
Author(s):  
Amadeusz Łaszcz ◽  
Mariusz Hasiak ◽  
Jerzy Kaleta
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Temperature Dependence ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
Anisotropy Energy ◽  
Ferromagnetic Shape Memory Alloys ◽  
Effective Anisotropy ◽  
Effective Anisotropy Constant ◽  
Ferromagnetic Shape Memory

The temperature dependence of magnetocrystalline anisotropy was investigated in detail for the polycrystalline Ni50Mn25Ga25, Ni50Mn25Ga20Ti5 and Ni50Mn25Ga20Gd5 ferromagnetic shape memory alloys in the temperature range of 50–400 K. The effective anisotropy constant was estimated from a series of high field magnetization curves based on the fitting procedure according to the law of approach to magnetic saturation. The low temperature martensitic phase was found to have a significantly higher anisotropy energy in comparison to a high temperature austenitic phase, which was observed through a sudden, distinct drop of anisotropy energy. The calculated values of the effective anisotropy constant were comparable to the results published by other authors. Moreover, the strong influence of chemical composition on the first-order phase transition and the second-order ferromagnetic to the paramagnetic transition was revealed. Finally, the strong coupling between the temperature dependence of the coercive field and the temperature dependence of magnetocrystalline anisotropy was also shown and discussed in the present study.

Preparation and Research of α-Fe/Montmorillonite Magnetic Material

2014 ◽  
Vol 809-810 ◽  
pp. 433-437
Author(s):  
Cheng Cheng Shi ◽  
Long Gui Peng ◽  
Zhi Wang
Keyword(s):  
Magnetic Material ◽  
Particle Size ◽  
Composite Material ◽  
Saturation Magnetization ◽  
Average Particle Size ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Layer Spacing ◽  
Particle Size Analyzer

α-Fe/montmorillonite (MMT) magnetic material was successfully prepared by the in-situ pillared-reduction method. The composite material was characterized by X-ray diffraction (XRD), laser particle size analyzer and other instruments. The magnetic property was researched by saturation magnetization. The results showed that: when 0.1mol/L hydroxyl-Fe was added as pillared agent, hydroxyl-Fe and cation of the MMT exchanged, leading to the inter-layer spacing expanded to 1.41nm and reached saturated pillared point. MMT interlayer hydroxyl-Fe was completely restored to α-Fe grains of 116nm when reducing agent was 0.2mol/L and produced α-Fe/MMT composite material. The average particle size of the composite was 5.529μm, the specific saturation magnetization was 0.812emu/g (9×103A/moutside magnetic field) and exhibited ferromagnetism.

scholarly journals Structural and Magnetic Properties of Nanosized Barium Hexaferrite Powders Obtained by Microemulsion Technique

2010 ◽  
Vol 159 ◽  
pp. 57-62 ◽  
Author(s):  
Tatyana Koutzarova ◽  
Svetoslav Kolev ◽  
Kornely Grigorov ◽  
Chavdar Ghelev ◽  
Andrzej Zaleski ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Cetyltrimethylammonium Bromide ◽  
Room Temperature ◽  
Average Particle Size ◽  
Barium Hexaferrite ◽  
Anisotropy Field ◽  
Microemulsion System ◽  
Average Particle ◽  
Crystalline Anisotropy ◽  
Magneto Crystalline Anisotropy

Thin hexagonal barium hexaferrite particles synthesized using the microemulsion technique were studied. A water-in-oil reverse microemulsion system with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, n-butanol as a co-surfactant, n-hexanol as a continuous oil phase, and an aqueous phase were used. The microstructural and magnetic properties were investigated. The particles obtained were mono-domain with average particle size 280 nm. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The saturation magnetization was 48.86 emu/g and the coercivity, 2.4 x 105 A/m at room temperature. The anisotropy field Ha and magneto-crystalline anisotropy K1 were 1.4 x 106 A/m and 2.37 x 105 J/m3, respectively.

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