Spherical Iron Research Articles

Motion characteristics of a charged metal particle in insulating oil under flow state

Problems due to discharge by charged metal particles in insulating oil under flow state are examined in this study. The motion characteristics of a charged metal particle in a horizontal transformer oil tract are investigated, and a mechanical model of a charged metal particle under flowing oil and an AC field is proposed. The particle's equations of motion are numerically solved using the fourth‐order Runge–Kutta computational algorithm. The trajectory of a spherical iron particle in typical motion state under flowing oil and AC field is simulated. The influence on the motion characteristics of a charged metal particle in terms of the oil flow rate, electric field strength of the oil tract, particle scale, initial state, and particle rotation is analyzed. Results reveal that when a charged metal particle is moving fast along the direction of oil tract flow, reciprocating oscillation simultaneously occurs in the vertical direction. Its trajectory is significantly affected by the oil flow rate, the electric field strength of the oil tract, particle scale, initial state, and particle rotation. Moreover, the degree of oscillation of the charged metal particle may be the main cause of degradation of the insulating oil under flow state. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

One-Step Facile Synthesis of Highly Magnetic and Surface Functionalized Iron Oxide Nanorods for Biomarker-Targeted Applications.

We report a one-step method for facile and sustainable synthesis of magnetic iron oxide nanorods (or IONRs) with mean lengths ranging from 25 to 50 nm and mean diameters ranging from 5 to 8 nm. The prepared IONRs are highly stable in aqueous media and can be surface functionalized for biomarker-targeted applications. This synthetic strategy involves the reaction of iron(III) acetylacetonate with polyethyleneimine in the presence of oleylamine and phenyl ether, followed by thermal decomposition. Importantly, the length and diameter as well as the aspect ratio of the prepared IONRs can be controlled by modulating the reaction parameters. We show that the resultant IONRs exhibit stronger magnetic properties compared to those of the widely used spherical iron oxide nanoparticles (IONPs) at the same iron content. The increased magnetic properties are dependent on the aspect ratio, with the magnetic saturation gradually increasing from 10 to 75 emu g-1 when increasing length of the IONRs, 5 nm in diameter, from 25 to 50 nm. The magnetic resonance imaging (MRI) contrast-enhancing effect, as measured in terms of the transverse relaxivity, r2, increased from 670.6 to 905.5 mM-1 s-1, when increasing the length from 25 to 50 nm. When applied to the immunomagnetic cell separation of the transferrin receptor (TfR)-overexpressed medulloblastoma cells using transferrin (Tf) as the targeting ligand, Tf-conjugated IONRs can capture 92 ± 3% of the targeted cells under a given condition (2.0 × 104 cells/mL, 0.2 mg Fe/mL concentration of magnetic materials, and 2.5 min of incubation time) compared to only 37 ± 2% when using the spherical IONPs, and 14 ± 2% when using commercially available magnetic beads, significantly improving the efficiency of separating the targeted cells.

Magneto-dynamic analysis of sandwiches composed of a thin viscoelastic-magnetorheological layer

This study’s relevance lies in the possibility of obtaining a smart sandwich structure with controllable dynamic properties, without compromising the main characteristics of conventional thin viscoelastic sandwiches. The proposed sandwich is composed of a micron-size viscoelastic-magnetorheological layer, which is obtained by adding spherical iron particles to a viscoelastic layer. Thin sandwiches with identical base layers and a viscoelastic core, with and without magnetic particles, are fabricated. Both the viscoelastic sandwich structure and viscoelastic-magnetorheological sandwich structure are experimentally characterised by a forced vibration test with resonance in a bandwidth between 0 and 1 kHz. This work analyses the influence of adding iron particles to obtain a smart thin sandwich. In addition, the vibrational response of the viscoelastic-magnetorheological sandwich structure under an external partial magnetic field, and the controllability of its dynamic properties by means of the magnetic field intensity and position, are studied.

Extended optical theorem in isotropic solids and its application to the elastic radiation force

In this article, we derive the extended optical theorem for the elastic-wave scattering by a spherical inclusion (with and without absorption) in a solid matrix. This theorem expresses the extinction cross-section, i.e., the time-averaged power extracted from the incoming beam per its intensity, regarding the partial-wave expansion coefficients of the incident and scattered waves. We also establish the connection between the optical theorem and the elastic radiation force by a plane wave in a linear and isotropic solid. We obtain the absorption, scattering, and extinction efficiencies (the corresponding power per characteristic incident intensity per sphere cross-section area) for a plane wave and a spherically focused beam. We discuss to which extent the radiation force theory for plane waves can be used to the focused beam case. Considering an iron sphere embedded in an aluminum matrix, we numerically compute the scattering and elastic radiation force efficiencies. The radiation force on a stainless steel sphere embedded in a tissue-like medium (soft solid) is also computed. In this case, resonances are observed in the force as a function of the sphere size parameter (the wavenumber times the sphere radius). Remarkably, the relative difference between our findings and previous lossless liquid models is about 100% in the long-wavelength limit. Regarding some applications, the obtained results have a direct impact on ultrasound-based elastography techniques and ultrasonic nondestructive testing, as well as implantable devices activated by ultrasound.

Preparation of iron oxide nanoparticles doped by chromium for application in water–gas shift reaction

An efficient preparation method of chromium-doped iron oxide nanoparticles of controlled size, chromium content and catalytic activity was developed. The catalysts were synthesized in an acidic hydrolysis of ferric chloride in order to obtain suspensions of spherical iron oxide nanoparticles with an average size of 10 and 100nm. After purification, the suspensions were transformed into powders. Afterwards, by a wet-impregnation and calcination chromium cations were incorporated to the nanoparticle structure without changing their size. The catalysts were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption (BET) and scanning electron microscopy (SEM). The activity of obtained samples was tested in a high temperature water gas shift reaction (HT-WGS) and compared with the results gained for chromium-free nanoparticles of similar sizes. The analysis of Raman spectra revealed that at elevated temperature iron hydroxyoxides are transformed to hematite (α-Fe2O3) and then, under catalytic conditions, to magnetite (Fe3O4) which is an active phase in the HT-WGS reaction. The chromium incorporated into the nanoparticles prevented a thermal sintering of nanocrystals, leading to an efficient catalyst performance. It was also shown that chromium-doped α-Fe2O3 nanoparticles of the size of 100nm, after the transformation to the magnetite phase, allowed to obtain a high carbon oxide conversion approaching the thermodynamic limit for temperatures above 500°C .

Spin waves on chains of YIG particles: dispersion relations, Faraday rotation, and power transmission

We calculate the dispersion relations for magnon waves on a periodic chain of spherical or cylindrical Yttrium Iron Garnet (YIG) particles. We use the quasistatic approximation, appropriate when $kd \ll 1$, where $k$ is the wave number and $d$ the interparticle spacing. In this regime, because of the magnetic dipole-dipole interaction between the localized magnetic excitations on neighboring particles, dispersive magnon waves can propagate along the chain. The waves are analogous to plasmonic waves generated by electric dipole-dipole interactions between plasmons on neighboring metallic particles. The magnon waves can be longitudinal ($L$), transverse ($T$), or elliptically polarized. We find that a linearly polarized magnon wave undergoes a Faraday rotation as it propagates along the chain. The amount of Faraday rotation can be tuned by varying the off-diagonal component of the permeability tensor. We also discuss the possibility of wireless power transmission along the chain using these coupled magnon waves.

A new three-dimensional magneto-viscoelastic model for isotropic magnetorheological elastomers

In this work, a four-parameter fractional derivative viscoelastic model was developed to describe the dynamic shear behaviour of magnetorheological elastomers (MREs) as a function of the matrix, particle content and magnetic field. The material parameters were obtained from experimental data measured with a Physica MCR 501 rheometer from the Anton Paar Company, equipped with a magnetorheological cell. The synthetised isotropic MRE samples were based on room-temperature vulcanising silicone rubber and spherical carbonyl iron powder micro particles as fillers, and seven volumetric particle contents were studied. The influence of particle contents was included in each parameter of the four-parameter fractional derivative model. The dependency of the storage modulus as a function of an external magnetic field (magnetorheological (MR) effect) was studied, and a dipole–dipole interaction model was used. A new three-dimensional magneto-viscoelastic model was developed to couple the viscoelastic model, the particle-matrix interaction and the magneto-induced modulus model, which predicts the influence of the magnetic field and the particle content in the MR effect of isotropic MREs.

Rheological properties of dimorphic magnetorheological gels mixed dendritic carbonyl iron powder

Magnetorheological gels typically are colloids of spherical micrometer magnetic particles dispersed in a high-viscosity polymer matrix. However, some major parameters of this kind of mono-disperse magnetorheological gel, such as the shear storage modulus and yield stress, cannot meet the needs of practical engineering application. In this study, a systematic experiment was investigated on the use of dendritic carbonyl iron particles to enhance the comprehensive performance in conventional (microsphere-based) magnetorheological gels formulated in polyurethane matrix. Two kinds of carbonyl iron particles that have very similar magnetic properties but very different morphologies (one is spherical and the other is dendritic) are employed. The dimorphic magnetorheological gels were prepared by adding dendritic carbonyl iron particles into the conventional spherical carbonyl iron particle–based magnetorheological gel and a series of dimorphic magnetorheological gel samples were prepared. The magnetorheological properties of those samples, both under oscillatory and rotational shear rheometry, were systematically tested. It was found that the dendritic carbonyl iron particle additives can significantly improve the shear storage modulus and response time of the dimorphic magnetorheological gels compared with conventional magnetorheological gels. Meanwhile, when the mass ratio of dendritic particles to carbonyl iron particles is 25% and 50%, the shear stress, static shear yield stress, and dynamic shear yield stress of dimorphic magnetorheological gels can also be greatly enhanced.

Microwave absorbing properties of flake-shaped carbonyl iron/reduced graphene oxide/epoxy composites

Microwave absorbers are used in a wide range of fields such as radar-cross section (RCS) reduction for stealth aircrafts, electromagnetic interference (EMI) reduction for electronic products and health protection for human. In this study, the flake-shaped carbonyl iron (FCI) powder was obtained from raw spherical carbonyl iron (SCI) powder by ball milling for 60h. The SCI powder was mixed with reduced graphene oxide (rGO) and then ball-milled for 60h to obtain rGO/FCI composite particles. Flake-shaped rGO/FCI particles have length of 1–20μm, thickness of 0.3–1μm, and aspect ratio of 1–60. The electromagnetic properties (ε′, ε′′, μ′, μ′′) of rGO/FCI/epoxy composite absorbers were measured by the transmission/reflection method in the frequency range of 2–18GHz for three samples with 50wt% of SCI, FCI and rGO/FCI particles, respectively. The results show that the values of permittivity and permeability both increase after ball-milling treatment. Compared with FCI/epoxy composite, the rGO/FCI/epoxy composite absorber exhibits higher dielectric loss and lower reflection loss. For absorbers with the same thickness, the rGO/FCI/epoxy composite shows better reflection loss with the target frequency shifting to the lower frequency region. For 50wt% of rGO/FCI/epoxy absorber with a thickness of 2mm, the minimum reflection loss reaches −32.3dB at matching frequency of 11.0GHz.

A PZT Actuated Triple-Finger Gripper for Multi-Target Micromanipulation

This paper presents a triple-finger gripper driven by a piezoceramic (PZT) transducer for multi-target micromanipulation. The gripper consists of three fingers assembled on adjustable pedestals with flexible hinges for a large adjustable range. Each finger has a PZT actuator, an amplifying structure, and a changeable end effector. The moving trajectories of single and double fingers were calculated and finite element analyses were performed to verify the reliability of the structures. In the gripping experiment, various end effectors of the fingers such as tungsten probes and fibers were tested, and different micro-objects such as glass hollow spheres and iron spheres with diameters ranging from 10 to 800 μm were picked and released. The output resolution is 145 nm/V, and the driven displacement range of the gripper is 43.4 μm. The PZT actuated triple-finger gripper has superior adaptability, high efficiency, and a low cost.

The enhanced MR performance of dimorphic MR suspensions containing either magnetic rods or their non-magnetic analogs

A co-precipitation method was used to prepare non-magnetic rod-like ferrous oxalate dihydrate (Fe2CO4 · 2H2O) particles that were further turned into iron oxide (Fe3O4) magnetic rod-like particles. A simple precursor-assisted thermal decomposition technique enabled the preservation of the morphology and size of the precursor ferrous oxalate dihydrate particles, thus allowing their magnetic analogs to be obtained. Both types of rod-like particles were used as an additive together with spherical carbonyl iron (CI) particles in novel dimorphic magnetorheological (MR) suspensions. Controlled shear rate mode experiments were performed using a rotational rheometer with a source of an external magnetic field in order to investigate their MR behavior. Moreover, the properties of the novel prepared dimorphic MR (DMR) suspensions were compared with conventional MR suspensions based on spherical CI microparticles. It was found that the DMR suspensions exhibit enhanced MR performance as well as enhanced sedimentation stability in comparison with the MR suspension based on pure CI. The dimorphic suspensions containing magnetic rod-like additives further exhibited significant MR hardening at low shear rates. The properties of CI-based suspensions can be thus optimized by using various additive substances.

Neutron spectra measurement and calculations using data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 in iron benchmark assemblies

The leakage neutron spectra measurements have been done on benchmark spherical assemblies - iron spheres with diameter of 20, 30, 50 and 100 cm. The Cf-252 neutron source was placed into the centre of iron sphere. The proton recoil method was used for neutron spectra measurement using spherical hydrogen proportional counters with diameter of 4 cm and with pressure of 400 and 1000 kPa. The neutron energy range of spectrometer is from 0.1 to 1.3 MeV. This energy interval represents about 85 % of all leakage neutrons from Fe sphere of diameter 50 cm and about of 74% for Fe sphere of diameter 100 cm. The adequate MCNP neutron spectra calculations based on data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 were done. Two calculations were done with CIELO library. The first one used data for all Fe-isotopes from CIELO and the second one (CIELO-56) used only Fe-56 data from CIELO and data for other Fe isotopes were from ENDF/B-VII.1. The energy structure used for calculations and measurements was 40 gpd (groups per decade) and 200 gpd. Structure 200 gpd represents lethargy step about of 1%. This relatively fine energy structure enables to analyze the Fe resonance neutron energy structure. The evaluated cross section data of Fe were validated on comparisons between the calculated and experimental spectra.

Ferrogels based on entrapped metallic iron nanoparticles in a polyacrylamide network: extended Derjaguin-Landau-Verwey-Overbeek consideration, interfacial interactions and magnetodeformation.

A new kind of ferrogel with entrapped metallic iron nanoparticles causing unusual magnetodeformation is presented. Crosslinked polyacrylamide (PAAm) based ferrogels embedded with iron nanoparticles (MNPs) were synthesized by free radical polymerization in aqueous medium. Spherical iron MNPs with average diameter 66 nm were synthesized by the electrical explosion of wire and modified by interfacial adsorption of linear polyacrylamide (LPAAm). Extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) calculations based on the superposing of van der Waals, electrostatic, steric, and magnetic contributions showed that polymeric encapsulation of nanoparticles by LPAAm is one of the most suitable pathways for preparing stable aqueous dispersions of iron nanoparticles. Microcalorimetry confirmed the presence of strong interfacial adhesion forces between LPAAm chains and the surface of iron nanoparticles. By keeping the same crosslinking density of a polymer network (i.e. 100 : 1, monomer to crosslinker ratio) and varying the initial monomer concentration, an influence of the extent of polymer network reticulation on the mechanical properties and subsequently, magneto-elastic properties was demonstrated. It was found that the upper limit of the shear modulus for the synthesis of a new kind of polyacrylamide based ferrogel to exhibit any usable magnetodeformation under the application of a uniform external magnetic field of 420 mT is ca. 1 kPa. Magnetodeformation of cylindrical ferrogel samples was observed in the form of an overall volume contraction accompanied by a homogeneous decrease in all dimensions. The deformation was found to be maximum (around 10%) for the aspect ratio of 1/1 and it was lower and similar for the samples with 1/2 and 2/1 aspect ratios. Such a type of magnetic response is significantly different from the behavior observed in the existing reports on ferroelastomers.

Benchmark integral neutron experiments for Fe, Be and C with DT neutron by liquid scintillation detector

The measurements of iron, beryllium and carbon sphere neutron leakage spectra using BC501A detector by DT neutron source are presented. The experiments were carried out in Institute of Nuclear Physics and Chemistry (INPC), China. Neutron leakage spectra in a wide energy range at angles of 0° and 30° from the direction of incident deuteron beam were obtained. The results show the leakage neutron flux decreases notably with the spherical shell increasing when neutron energy >10MeV. When neutron energy <6MeV the leakage neutron distribution tends to lower energy side with the shell increase. The total uncertainty evaluation of the neutron spectra is also provided: in the high-energy parts the uncertainty is about 5–7%, while in the low-energy parts the uncertainty is about 7–9%. In order to compare the experiment results a Monte-carlo calculation was made using the MCNP5 Code with the ENDF/B-VII.1 nuclear data files.

Tridentate (O,N,O) ligands as potential chelator compounds for iron overload

Iron(III) complexes of three ligands (H2calm, H3anth and H3hyphS) have been studied by means of potentiometric, various spectroscopic (UV–Vis, 1H NMR, IR), mass spectrometric, electrochemical and computational (DFT) methods. For investigation of the selectivity of these ligands the studies were completed by characterization of their iron(II)-, copper(II)-, manganese(II)-, calcium(II)- and aluminum(III)-complexes. All three ligands are able to bind iron(III) in strong acidic pH via (O−,N,O−) donor set. The coordination of two ligands in the bis(ligand)complexes saturates the coordination sphere of iron(III) and the meridonial arrangement was supported by DFT methods. The ligands with (O−,N,O−) donor set are able to bind iron(III) selectively at physiological pH. Moreover, the electrochemical parameters of complexes rule out that iron(III) complexes can initialize the formation of reactive oxygen species. These results clearly show that this type of ligands with (O−,N,O−) donor set is suitable for the designing of new chelator molecules with possible application to iron overload.

Submicrometer‐Sized Spherical Iron Oxide Particles Fabricated by Pulsed Laser Melting in Liquid

SUMMARYSubmicrometer‐sized spheres of iron oxide were obtained by laser irradiation of cuboidal Fe3O4 particles dispersed in ethanol, acetone, and toluene. Sphere formation condition and sphere size are explained based on a relationship between particle size and laser fluence required for solid–liquid phase transition of Fe3O4, which is calculated by equating the melting enthalpy and the optically absorbed energy derived from Mie theory. FeO was partially formed by laser irradiation at 200 mJ pulse−1 cm−2 in ethanol, acetone, and toluene. The reduction reaction is not simply due to thermal decomposition of Fe3O4, but due to the reduction by chemical species generated from solvent surrounding Fe3O4 particles melted by laser irradiation. Ethanol was more reductive than the other two solvents; Fe is formed even at 200 mJ pulse−1 cm−2. This is probably due to chemical reactivity of produced iron oxides and chemical species transiently generated from solvent.

Influence of carbonyl iron particle coating with silica on the properties of magnetorheological elastomers

In this paper, the influence of encapsulating carbonyl iron particles with various silica coatings on the properties of magnetorheological elastomers (MREs) was investigated. A soft styrene–ethylene–butylene–styrene thermoplastic elastomer was used as the composite’s polymer matrix. Spherical carbonyl iron powder (CIP) acted as the ferromagnetic filler. In order to improve the metal–polymer interaction, carbonyl iron particles were coated with two types of single and six types of double silica layers. The first layer was created through a TMOS or TEOS hydrolysis whereas the second one was composed of organosilanes. The mechanical properties of MREs containing 38.5 vol% of CIP were analysed under dynamic loading conditions. To investigate the magnetorheological effect in these composites, a 430 mT magnetic field, generated by an array of permanent magnets, was applied during testing. The results revealed that the magnetomechanical response of the MREs differs substantially, depending on the kind of particle coating.

Electrophoretic deposition of spherical carbonyl iron particles on carbon fibers as a microwave absorbent composite

Carbonyl iron (CIPs) micron size spherical particles were deposited on carbon fibers by electrophoretic deposition method (EPD). A well stabilized suspension of CIPs was prepared in acetone-ethanol media and two different stabilizer of Iodine and Trietanolamine (TEA) were used to investigate stability of suspension. X-ray Diffractometer (XRD) was employed to study structure of CIPs, CFs and CFs/CIPs composite. Field Emission Scanning Electron Microscopy (FE-SEM) images were taken to see the morphology of CFs and deposited particles. Dynamic Light Scattering (DLS) and zeta potential test were carried out to study the stability of particles and also to see the average particle size of powder. To investigate magnetic and reflection loss properties, Vibrating Sample Magnetometer (VSM) and Vector Network Analyzer (VNA) were used, respectively. Uniformly coated fibers were selected to make composites and results revealed that the best Reflection Loss (RL) was related to CFs coated for 20 minutes in a bath containing iodine with a layer thickness of 2mm. Maximum recorded RL was found to be -13.8dB at frequency of 9.22GHz.

A comparison of field-dependent rheological properties between spherical and plate-like carbonyl iron particles-based magneto-rheological fluids

This work proposes different sizes of the plate-like particles from conventional spherical carbonyl iron (CI) particles by adjusting milling time in the ball mill process. The ball mill process to make the plate-like particles is called a solid-state powder processing technique which involves repeated welding, fracturing and re-welding of powder particles in a high-energy ball mill. The effect of ball milling process on the magnetic behavior of CI particles is firstly investigated by vibrating sample magnetometer. It is found form this investigation that the plate-like particles have higher saturation magnetization (about 8%) than that of the spherical particles. Subsequently, for the investigation on the sedimentation behavior the cylindrical measurement technique is used. It is observed from this measurement that the plate-like particles show slower sedimentation rate compared to the spherical particles indicating higher stability of the MR fluid. The field-dependent rheological properties of MR fluids based on the plate-like particles are then investigated with respect to the milling time which is directly connected to the size of the plate-like particles. In addition, the field-dependent rheological properties such as the yield stress are evaluated and compared between the plate-like particles based MR fluids and the spherical particles based MR fluid. It is found that the yield shear stress of the plate-like particles based MR fluid is increased up to 270% compared to the spherical particles based MR fluid.

Analysis of Air Particulate Emissions Collected Downwind of an Automobile Shredding Operation: Implications for the Environment and Human Health

ABSTRACTThe disposal of materials at the end of their lifecycle, especially for complex manufactured products, presents challenges in terms of both protecting the environment and human health. In particular, used automobiles are disposed of by removal of various component parts, followed by shredding. In this study, air particulates were collected over several days by DRUM impactor downwind of an automobile shredding plant, size separated, and analyzed by scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive x-ray spectroscopy (EDXS), in order to determine their particle size distribution and corresponding chemical composition. Results for larger particles, ranging in size from 2.5 to 10.0 μm, showed mainly diatoms and salts, from the plant’s ocean side location, and aluminosilicates, consistent with geological sources. As particle size decreased from 10 μm to 0.09 μm, particle loading decreased, and composition shifted to mainly oxygen and sulfur, indicative of sulfates, which along with nickel and vanadium that were detected, could be attributed to emissions from nearby shipping traffic. Iron was found to be present, including in spherical particles that were ∼ 2 μm in diameter, indicating they originated from a high temperature process. Spherical iron particles also were found to correlate with plant operations, making them a useful “tracer” material for plant emissions. Lead, cerium, barium, chromium and zinc were also detected and their possible correlation to plant feedstocks is discussed. The implications of these results for the environment, particularly soil and water deposition, and for human health as a result of inhalation, are discussed.