Concentration Of Ferromagnetic Particles Research Articles

Treatment of Water Polluted by Oil Spill by Ferromagnetic Particles

Water constitutes 71% of the Earth's surface, and up to 60% of the human body. The amount of water that humans consume, and need depends on the age, gender and the location. According to many studies, oil spill is considered as one of the most common environmental disasters, resulting in the destruction of ecosystems and significant losses for the economies of the countries that suffer from leaked oil, not only because of the price of the leaked oil but also because of the extinction of many marine organisms that live in these environments. The Kingdom of Saudi Arabia exports a huge amount of crude oil, varies between 6.935 and 7.737 million barrels per day, leading to rise oil pollution that may harm the vital marine environment. The current paper aims to examine the effect of micro and nano-ferromagnetic in the treatment of water polluted by oil spill. The method is based on mixing the oil with ferromagnetic particles and using the neodymium magnets to separate the particles from the oil. The experiment was repeated by changing the concentration of ferromagnetic particles, that are able to purify water from oil at rates ranging from 154 for microparticles to 185 for nanoparticles. The properties of seawater treated with ferromagnetic particles were identified in both parts by measuring the acidity value and identifying the compounds present in the samples, followed by mechanical experimentation. Results showed the efficacy of purifying seawater from oil leakage using ferromagnetic nanoparticles as well as the extent to which ferromagnetic materials can be separated from oil by examining the components of the water after purification. Also, this method is safe, highly efficient, and cheap for purifying sea water from oil pollution. In addition, the acidity of the water was not affected using ferromagnetic particles, as it ranged around 8.5 for all samples.

ИССЛЕДОВАНИЕ ГЕРМЕТИЗИРУЮЩЕЙ СПОСОБНОСТИ КОМБИНИРОВАННОГО МАГНИТОЖИДКОСТНОГО УПЛОТНЕНИЯ ПОДШИПНИКОВЫХ УЗЛОВ

The purpose of the research is to increase the efficiency of hermetic ability of bearing assemblies by using com-bined ferrofluidic sealed. The research objective is theoretic justification of the maximum concentration of ferro-magnetic particles in fluid, investigation of hermatic ability of a combined ferrofluidic seal under conditions of tem-perature changing and speed of a shaft rotation of packing bearing assembly. The study of hermetic ability of lip and ferro-fluidic sealed was carried out on a test bench, allowing to determine the packing ability of seals both in static and dynamic mode. On the basis of theoretical data, formulas were determined to find the maximum concen-tration of hard and magnetic phases in a ferrofluid, and its composition based on a polyethylsiloxane liquid PES-5 with a 40 kA/m saturation magnetization and a 1.2 Pas dynamic viscosity coefficient was developed. A mixture of magnetite with powdered iron was used as the ferromagnetic phase. Oleic acid was used as a surfactant. Studies to determine hermetic capacity have shown a higher efficiency of the combined ferrofluidic seal compared to the lip one. During static test within the temperature range between 20 to 600C, the critical pressure difference of the com-bined seal was 4-16% higher than that of the lip seal. Temperature increase of the bearing assembly from 20 to 1200C causes a decrease in critical pressure difference of up to 50%. This is due to a decrease in the sedimentative stability of the magnetic fluid as a result of an increase in temperature. Studies show that the combined ferrofluidic seal has a higher hermetic tightness at the starting torque than the standard lip seal. In contrast to the lip seal (which tends to lose its tightness at the starting torque), no leakage of pressure fluid from the sealed unit was observed of the com-bined ferrofluidic one with a pressure drop of 0.094 MPa. The results obtained allow reasonably select the concen-tration of magnetic particles in the ferrofluid, and also prove the prospects of replacing standard lip seals with com-bined ferrofluidic ones.

A method to approach constant isotropic permeabilities and demagnetization factors of magneto-rheological elastomers

The use of non-conventional materials is nowadays of much interest in scientific community. Magneto-rheological elastomers are hybrid materials, which in presence of magnetic fields state a change in their mechanical properties. They are composed by an elastomeric matrix with embedded magnetic particles. One of the most attractive features of these materials is that as soon as the magnetic field is removed from the material, the original mechanical properties are completely recovered, with negligible differences in comparison to the original state. This paper focuses on the study of magnetic characteristics of these smart materials, such as relative permeability and demagnetizing factors, for samples with different volume concentration of ferromagnetic particles.

Investigation of a Magnetic Field-Assisted Digital-Light-Processing Stereolithography for Functionally Graded Materials

Abstract Stereolithography (SLA) is one of the most efficient additive manufacturing (AM) methods in terms of dimensional resolution and accuracy. The use of multiple or functionally graded materials in this process can broaden the design space for applications such as sensors and biomedical implants. However, it is still challenging to fabricate such materials using SLA. In this study, we propose a method for fabrication of functionally graded materials with embedded magnetic particles using digital-light-processing SLA in a single step. Magnetite (Fe3O4) particles with an approximate diameter of 300 nm were mixed with a diluted photocurable resin, and used in fabrication of the samples. A digital-light-processing SLA printer was modified to allow integration of a magnet holder above the print bed. Magnet holders with three different configurations of magnets were built and used to fabricate parts with controlled distribution of magnetic particles. Several parts have been printed and characterized by evaluating the concentration of ferromagnetic particles in different regions based on image analysis. The results of this study show that field assisted digital-light-processing SLA can be used to fabricate functionally graded materials with embedded magnetite particles. The resulting concentration of the particles depends on the strength and surface area of the magnets, and the distance between the magnets and the print bed. Experimental results are also used to verify a Finite Element model, which is developed to understand the effect of magnet location on particle concentration. The feasibility of the proposed process has been verified and this process can be used in additive manufacturing of magnetic field-responsive smart polymeric structures.

Transient Magnetic Model of Magnetorheological Damper and Its Experimental Verification

The present paper deals with the transient magnetic model of the magnetorheological (MR) damper and its experimental verification. The response time of MR damper affects the quality of semi-active control of this damper. The lower the response time, the higher the system efficiency. The most important part of the response time of the MR damper is the response time of magnetic field of the MR damper which can be determined by transient magnetic model. The transient magnetic model was created by the software Ansys Electromagnetics 17.1 as 2D axisymmetric and verified by measurement of magnetic field in the gap of MR damper piston. The maximum difference between the model and the experiment was 28 %. The response time depends on the electric current in the coil of MR damper. The transient magnetic model was used for determination of influence of MR fluid type, material of cover and material of magnetic circuit on the response time of magnetic field of MR damper. The type of MR fluid has a significant influence on the response time. The lower the mass concentration of ferromagnetic particles, the lower the response time of magnetic field. A material selection of magnetic circuit is always a trade-off between the response time and the maximum magnetic flux density (dynamic force range) in the gap of the MR damper. According to the verified transient magnetic model, it is possible to find a suitable material of magnetic circuit for specific application (response time).

Tuning the Spin-Alignment of Interstitial Electrons in Two-Dimensional Y2C Electride via Chemical Pressure.

We report that the spin-alignment of interstitial anionic electrons (IAEs) in two-dimensional (2D) interlayer spacing can be tuned by chemical pressure that controls the magnetic properties of 2D electrides. It was clarified from the isovalent Sc substitution on the Y site in the 2D Y2C electride that the localization degree of IAEs at the interlayer becomes stronger as the unit cell volume and c-axis lattice parameter were systematically reduced by increasing the Sc contents, thus eventually enhancing superparamagnetic behavior originated from the increase in ferromagnetic particle concentration. It was also found that the spin-aligned localized IAEs dominated the electrical conduction of heavily Sc-substituted Y2C electride. These results indicate that the physcial properties of 2D electrides can be tailored by adjusting the localization of IAEs at interlayer spacing via structural modification that controls the spin instability as found in three-dimensional elemental electrides of pressurized potassium metals.

Estimation of solids circulation rate through magnetic tracer tests

This work assesses the solids circulation rate in a circulating fluidized bed cold model based on measuring the particles mean residence time (τ). The tracking method detects fluid-dynamically similar ferromagnetic tracer particles, and is based on inductance changes of a coil due to changes in the concentration of ferromagnetic particles in its core. A section of the model was selected to perform the tracer measurement, such that the variations in the solids volumetric fraction and the solids velocity were negligible, and a correlation between the circulation rate and the mean residence time of solids could be established. The circulation rate was calculated in this manner for a range of operation conditions, variations of riser fluidization velocity and total inventory were performed. The results were validated measuring the circulation rate by the accumulation method as well, the results show a satisfactory correlation between the tracer and the accumulation methods. The magnetic tracer method appears thus to be suitable for the measurement of solids circulation rates in low temperature applications. This method offers as advantages the possibility for on-line measurement, good sensitivity, non-intrusiveness, cost efficiency, and does not require a calibration.

Characterization and magnetic properties of nanoparticles based on FePt solid solution with an oxide shell

Abstract We present the results of magnetic properties investigations of ferromagnetic nanoparticles which ensembled with ferromagnetic shell. The aim of this work is to study the connection of structure–phase composition and thermal treatment with the magnetic properties, partially, with the coercive force and the exchange bias field in a two-dimension spin system of core–shell type. It is found that the exchange bias field increases with the growth of the oxide shell thickness. This is realized by annealing in a dosed oxygen flow. The decrease of the coercive force with the increase of annealing temperature is connected with the concentration effect (the concentration of ferromagnetic particles decreases).

Inverse magnetorheological fluids.

We report a new kind of field-responsive fluid consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, those of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field application, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30% of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on the second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results.

Design of an Inductance Measurement System for Determination of Particle Residence Time in a Dual Circulating Fluidized Bed Cold Flow Model

A tracer impulse method is designed and implemented for determination of the residence time distribution (RTD) of particles in a cold flow model of a dual circulating fluidized bed chemical looping pilot plant. Ferromagnetic particles are used as a tracer. The method based on inductance measurements previously proved its suitability and convenience for determination of the concentration of ferromagnetic particles and the bed porosity. The current paper presents an improved system for the determination of inductance, based on an impedance circuit bridge. Injection and detection systems were designed and optimized for an extremely small amount of tracer, about 0.05% by mass. The system is entirely described, variables relevant for the attainment of an appropriate measurement are analyzed, and the first results of RTD experimentally determined are presented. Signals of high quality were obtained and successfully fitted to a simple model. The system shows a great capacity regarding the response time, quality ...

Measurement of ferromagnetic particle concentration for characterization of fluidized bed fluid-dynamics

A method based on indirect measurement of magnetic properties of solids is proposed and investigated to be implemented in existing cold flow models of fluidized beds as a system for the determination of bed density and particle residence time distribution. The current work reports the fundamental principles for the measurement method and presents a first approach to the practical implementation which is based on inductance measurement of a simple coil. The characterization of the materials is reported and the fluid-dynamic suitability of the chosen ferromagnetic tracer particles is confirmed. The results clearly show the reproducibility of the measurement and evidence the capability to measure the concentration of tracer particles in an accurate way. The bed density of a fluidized bed was successfully determined using the designed apparatus. The method proposed appears promising and easily implementable for measurements of void fraction, residence time distribution of solids (RTD) and circulation rate in fluidized bed cold flow models.

Simulation of flow behavior of particles in liquid–solid fluidized bed with uniform magnetic field

Abstract Flow behavior of solid phases is simulated by means of DEM–CFD in a liquid–solid fluidized bed with magnetization of preliminarily fluidized bed (LAST) mode along an axial uniform magnetic field. By changing the magnetic field strength, the distribution of particles is studied within the bed. The distributions of velocity and concentration of ferromagnetic particles are analyzed at the different magnetic field intensities. When the magnetic field strength is increased to a value at which the fluidization of strings starts, the particles are found to form straight-chain aggregates along the direction of the magnetic field. At very high magnetic field strengths, the defluidization is observed at which particles are fixed in the bed. Simulations indicate that the granular temperature of particles increases, reaches a maximum, and then decreases with the increase of magnetic-flux density. The moderate strength magnetic field gives a high fluctuation of particles. The predicted solid pressure increases with the increase of concentration of particles.

Advanced Maintenance of Rail Traction Motors Using a Magnetic Leakage Flux Technique

Asynchronous induction motors are actually the most used in rail vehicle traction chains. Although more reliable and robust than dc motors, they are vulnerable to insulation failures, particularly in dirty environments. The dirt accumulated inside motors is one the main causes of insulation failure. Excessive accumulation of dirt blocks in ventilation vents and motor air gap may lead to overheating and, in severe cases, abrasion of the insulation. Taking advantage of the peculiarities of environmental rail dirt (dirt with a high concentration of ferromagnetic particles), a new predictive technique has been developed which is able to detect the presence of excessive motor dirt in operating conditions. This new technique to determine the degree of contamination in the motor air gap is based on the measurement of magnetic leakage flux and its subsequent analysis in the frequency domain. The results of the technique make it possible to detect dirt accumulations early, before breakdown occurs and without the need to stop the machine.

The influence of intergranular interaction on the magnetization of the ensemble of oriented Stoner–Wohlfarth nanoparticles

The influence of interparticle interaction on the processes of magnetization reversal is considered for an ensemble of oriented Stoner–Wohlfarth nanoparticles. This is done through a solution of a kinetic equation describing the relaxation of the total magnetization to its equilibrium value in an effective mean field which includes a term proportional to the instantaneous value of the magnetization. It is shown that the interparticle interaction influences the temperature dependence of a coercive field. Under certain conditions, the presence of the interparticle interaction can lead to the formation of the so-called superferromagnetic state with the correlated directions of the magnetic moments of the particles. If the system is unable to come to the equilibrium during the time interval necessary to perform measurements, some measured quantities become dependent on the measurement time. It is shown that the blocking temperature Tb and the temperature dependence of coercive field at T<Tb are strongly dependent on a measurement time. At T>Tb, however, the coercivity, if exists, does not depend on the measurement time. The data of magnetostatic measurements, carried out on the (CoFeB)x–(SiO2)1−x nanogranular films with the concentration of ferromagnetic particles slightly lower than a percolation threshold, are in compliance with the results of the calculations.

SQUID magnetopneumography used to estimate the ferromagnetic particle content in the human lungs

A number of possibilities for quantifying the ferromagnetic particle contamination in human lungs with the help of RF SQUID system are studied. A tool for the analysis of the quantification of the measured data is developed. Moreover, the conditions for the calculation of the particle concentration in human lungs from the measured remanent magnetic induction are discussed. The theoretical calculations were verified by measuring on physical model of lungs. Lastly, the estimation of the concentration of ferromagnetic particles in the lungs of arc welders with contaminated lungs is addressed.

Some features of the magnetorheological effect

The Theological properties of magnetorheological suspensions (MRS) are investigated in a wide concentration range of particles of the disperse ferromagnetic phase in the presence of a magnetic field. It is shown that, along with an increase in the concentration of ferromagnetic particles, the range of control of the viscous stress increment in an MRS can be broadened by changing the size and shape of the ferromagnetic particles, introducing nonmagnetic particles into the dispersion medium as well as by heating the medium to the Curie temperature.

Optical and magneto-optical spectra of magnetic granular alloys

We present the results of the experimental and theoretical investigation of the optical and magneto-optical (MO) spectra of magnetic granular films (Co 70Fe 30) x Ag 1− x , Co x Ag 1− x , in the energy range 0.5-4.0 eV of incident light. The MO properties were investigated in the geometry of transverse Kerr effect. The MO spectra of granular alloys are quite different from the spectra of homogeneous films. The amplitude of Kerr signal and the MO spectra profile depend on the granular and matrix material, the concentration and the shape of the grains and the annealing temperature. We interpret the obtained spectra in the framework of the effective medium approximation that allows to make some conclusions about ferromagnetic particle concentration and their shape.

Fundamental theory for constitutive equation of viscoelastic conducting magnetic fluids.

A new complete set of basic equations for viscoelastic conducting magnetic fluids with internal rotation are derived by the thermodynamical method wherein free energy and dissipation function are used on the basis of kinematical balance equations in the polar theory. The basic equations and the constitutive equations obtained here are useful if the volume concentration of ferromagnetic particles in the magnetic fluids is increased. New constitutive equations for magnetization and polarization are obtained. The magnetization is related to the magnetic field, its change in time and the angular velocity of suspended particles. Furthermore, it is shown that the electromagnetic pressure is independent of the dissipative parts of magnetization and polarization.

Redistribution of ferromagnetic particle concentration in a magnetic fluid

It was found experimentally and explained theoretically that the magnetic field intensity affects the dependence of the redistribution of the ferromagnetic particle concentration on the magnetic field direction. The effect of the thermomagnetic force on redistribution of the ferromagnetic particle concentration was found experimentally and explained theoretically.

Determination of metallic iron in wear debris using a wear particle analyzer

A study was conducted to investigate the capability of a wear particle analyzer (WPA) in quantitatively determining the concentration of ferromagnetic particles in used lubricants. The effects of sample volume, particle size, particle type, sample flow rate and type of magnetic filter on the WPA reading have been determined using iron powders and an iron oxide suspended in oils, wear metals generated from a wear test machine and used oils from operational aircraft jet engines. Acid dissolution, solvent extraction and magnetometer techniques were used to examine the accuracy of the WPA. Filters made from micron steel fiber and compressed with a high force gave the highest WPA readout. The optimun sample volume was approximately 2 ml and the effective particle size captured by the WPA filter was less than 3 μm. Higher flow rates improved the results for iron powders. The study reveals that the WPA is an adequate analytical tool for analyzing used oils for metallic iron particles and can be used to supplement other oil analysis techniques.