Particles In Magnetic Fluids Research Articles

Ultra-Sensitive, Rapid and On-Site Sensing Harmful Ingredients Used in Aquaculture with Magnetic Fluid SERS.

The integration of surface-enhanced Raman scattering (SERS) spectroscopy with magnetic fluid provides significant utility in point-of-care (POC) testing applications. Bifunctional magnetic–plasmonic composites have been widely employed as SERS substrates. In this study, a simple and cost-effective approach was developed to synthesize magnetic–plasmonic SERS substrates by decorating silver nanoparticles onto magnetic Fe3O4 nanoparticles (AgMNPs), which function both as SERS-active substrates and magnetic fluid particles. The strong magnetic responsivity from AgMNPs can isolate, concentrate, and detect target analytes from the irregular surface of fish skin rapidly. We fabricate a microfluid chip with three sample reservoirs that confine AgMNPs into ever smaller volumes under an applied magnetic field, which enhances the SERS signal and improves the detection limit by two orders of magnitude. The magnetic fluid POC sensor successfully detected malachite green from fish with excellent selectivity and high sensitivity down to the picomolar level. This work achieves a label-free, non-destructive optical sensing approach with promising potential for the detection of various harmful ingredients in food or the environment.

Experimental study and mathematical modelling of self-oscillation at the electrode-magnetic fluid interface in an electric field

The article describes a mathematical model of self-oscillation in the form of a boundary value problem for a nonlinear system of partial differential equations, with a numerical solution. The numerical results were compared to the experimental data to confirm the adequacy of the model. The model uses the classical system of differential equations of material balance, Nernst-Planck and Poisson equations without simplifications or fitting parameters. The aim of the article was to study the parameters of concentration self-oscillation in a layer of the dispersed phase particles of magnetic fluid at the interface with an electrode in an electric field. For this purpose, we developed a mathematical model, the consistency of which wasconfirmed by the corresponding physical mechanism.As a result of numerical experiments, we found the critical value of the potential jump after which self-oscillation began. We also determined the oscillation growth period and other characteristics of the process. We developed software called AutoWave01 with an intuitive user interface and advanced functionality for the study of self-oscillation in a thin layer of magnetic colloid.

In English

Сombination of properties of lectins and magnetically sensitive iron-containing nanocomposites (NC) for use in oncology is actual and promising from scientific and applied point of view. The aim of the research is to synthesize and to study new iron-containing NC and magnetic fluids containing bioactive bacterial lectin, promising for use as prototypes of new effective antitumor vector systems for targeted drug delivery and combined local therapy of cancer with minimized side effects on the body and improved compatibility with other remedies. To create vector systems, nanodisperse magnetite was synthesized by the Elmore reaction. The synthesis of aluminum-containing coating on the surface of Fe3O4 was carried out by double chemical modification with aluminum isopropylate. The obtained Fe3O4/Al2O3 NC was impregnated with sucrose solutions. Carbonization of the carbohydrate shell of NC was carried out in argon (500 °C). As a result, Fe3O4/Al2O3/C NC was obtained. The magnetic properties of nanostructures were measured using a laboratory vibration magnetometer of Foner type at room temperature. Adsorption immobilization of lectin was performed in 0.9 % NaCl solution in a dynamic mode at room temperature. Bacterial cytotoxic lectin of B. subtilis IMB B-7724 was used in the experiments. The amount of adsorbed substance (A) on the surface of nanocomposites was determined by measuring the concentration of lectin in the contact solutions before and after adsorption using a calibration graph. Measuring of the optical density and absorption spectra of lectin was performed on a spectrometer Lambda 35 UV/vis Perkin Elmer Instruments at λ = 280 nm. Standard techniques and equipment were used for biological research. The processes of adsorption immobilization of cytotoxic bacterial lectin of B. subtilis IMB B-7724 from physiologic saline on the surface of magnetite and carbon-containing Fe3O4/Al2O3/C NC were studied at room temperature. It has been found that the adsorption capacity of lectin on the surface of magnetite is 25.3 mg/g, and Fe3O4/Al2O3/C NC – 36.3 mg/g (at initial concentrations of lectin 0.06–0.4 mg/mL). The extraction extent of lectin R (%) was 12–38 % for magnetite and 46–67 % for Fe3O4/Al2O3/C NC. The dependence of the adsorption capacity on time was studied. A magnetic fluid (MF) based on single-domain Fe3O4, containing lectin was synthesized and investigated. Immobilization of lectin on MF particles was carried out in a dynamic mode at room temperature for 3 hours. The concentration of lectin in the composition of MF was 0.2 mg/mL. MF with immobilized lectin was further modified with PEG-2000. The synthesis of Fe3O4/ol.Na/lectin/PEG (ol.Na – sodium oleate) vector system was carried out in a dynamic mode for 3 hours. Modification of the surface of nanoparticles with polyethylene glycol was performed in order to increase the stability of the magnetic fluid, reducing the aggregation of particles. To determine the effect of experimental samples on the viability of MCF-7 cells in vitro, the following samples were prepared: Fe3O4/ol.Na/PEG (MF), CFe3O4 = 3 mg/mL; cytotoxic lectin of B. subtilis IMB B-7724 (CL), CCL = 0.2 mg/mL; nanobiocomposite (NBC). Nanobiocomposite based on MF and bacterial lectin was found to have a synergistic cytotoxic effect on MCF-7 human breast cancer cells, causing up to 40 % cell death. The IC50 values for the nanobiocomposite and lectin in relation to MCF-7 cells were 100 and 125 μg/mL, respectively. The results of research show that the combination of properties of lectins and magnetically sensitive iron-containing NC for use in oncology is a promising direction in creating new effective antitumor vector systems for targeted drug delivery and combined local therapy of cancer. The use of natural components in vector systems is a way to minimize the side effects on the body and improve compatibility with other antitumor remedies.

Interaction and orientation of non-magnetic particles in magnetic fluid in magnetic and electric fields

In this article, the processes of structuring non-magnetic microparticles of various shapes (spherical and cylindrical) placed in magnetic liquid are investigated. It was established that the equilibrium orientation of non-magnetic microparticles and structural formations from them in magnetic and electric fields is determined by the ratio of both field strengths and magnetic and electrical parameters of the carrier medium and material of non-magnetic inclusions. Analysis of mechanisms of interaction of non-magnetic filler particles and orientation of formed structures under the influence of magnetic and electric fields was carried out. It has been found that the action of a uniform magnetic field on a magnetic liquid with a dispersed non-magnetic filler leads to a significant anisotropy of the thermal conductivity coefficient - the difference in the thermal conductivity coefficient in the direction coinciding with the field strength vector and perpendicular to it can reach 25%. The analysis of the detected effect is made on the basis of ideas about the occurrence of structural anisotropy in such a medium due to the structural organization of non-magnetic filler particles in the magnetic field.

Numerical investigation of magnetic-field induced self-assembly of nonmagnetic particles in magnetic fluids

The underlying mechanisms of controlling the self-assembly of micro-size nonmagnetic particles (NPs) in magnetic fluids are essential for the manufacture, process and exploitation of nano-magnetic material. In this study, a multi-physical numerical model, which couples a distribution function correction-based immersed boundary lattice Boltzmann method (DFCIB-LBM) for fluid–structure interaction (FSI) and a self-correcting procedure of Poisson equation solver for magnetic field, is carried out to investigate such self-assembling behaviors and mechanisms. The interactions of two neighboring micro-size NPs placed in different distance and orientation, and the self-assembling behaviors of numerous micro-size NPs under uniform magnetic field are studied in details. The results demonstrate that the self-assembling behaviors are caused by the inverse magnetic effect, which can be adjusted by varying the concentration and size of NPs, permeability ratio, and the strength of external magnetic field. On the contrary, NPs in magnetic fluid affect their surrounding magnetic field and hinder the magnetization near the NP boundary region. These findings can provide a better understanding of the bottom-up fabrication of magnetic functional materials and devices.

Modelling of counter current imbibition phenomenon in two-phase fluid flows through fractured heterogeneous porous media under the effect of magnetic field

In this paper, the counter-current imbibition phenomenon is discussed in a fractured heterogeneous porous medium under the effect of magnetic field due to the presence of magnetic fluid particles in injected fluids as well as the effects of inclination, capillarity, relative permeability and the viscosity variation of native fluids on saturation rate and on the recovery rate are considered. The homotopy analysis method is used to derive an expression for finding the saturation profiles and to study the recovery rate of the reservoir with some interesting choices of parameters.

On the Role of Size Differences in Synchronized Motion of Magnetic Particles in Fluid: A Study on Trimers

Synchronized motion and pattern formation of magnetic particle aggregates in variable magnetic field is of growing interest from the point of view of both fundamental science and its applications. In this article, the role of size differences in synchronized motion of magnetic particles under external rotating magnetic field at low Reynolds number flow regimes is considered. Several different motion regimes are observed in simulations as a function of particle size differences and field rotation rate. Simulation indicates phase-like transitions between different motion regimes when particle size differences become significant. It is also shown that particle size differences permit the possibility of locomotion for particle aggregates which cannot be observed for uniform particle sizes.

Application of Amorphous Nanoparticle Fe-B Magnetic Fluid in Wastewater Treatment

Amorphous magnetic particles demonstrate excellent comprehensive properties and outstanding characteristics for numerous applications. In this report, magnetic crystalline Fe3O4 and amorphous Fe-B nanoparticles were successfully synthesized and introduced to prepare water-based magnetic fluids. The Fe3O4 and Fe-B particles are homogeneous nanoparticles with an average particle size of [Formula: see text][Formula: see text]nm. The shape of Fe-B amorphous nanoparticles is regular. The saturation magnetizations of Fe-B and Fe3O4 particles are 74 emu/g and 69 emu/g. The use of crystalline Fe3O4 magnetic fluid and amorphous Fe-B magnetic fluid in advanced treatment of high concentration organic wastewater was presented. The removal rate of chemical oxygen demand by using the amorphous Fe-B magnetic fluid reached 96%, about 16% higher than that by using the Fe3O4 magnetic fluid. Moreover, compared with Fe3O4 magnetic fluid, the treatment results demonstrate that the decolorizing effect by using the amorphous Fe-B magnetic fluid was 20% higher. It has been found that the nano-size Fe-B particles in magnetic fluid with amorphous structure led to high efficiency of wastewater treatment due to the catalytic activity.

Coupled heat transfer characteristics in a spiral groove mechanical seal lubricated by magnetic fluid

PurposeThe purpose of this study is to investigate the heat transfer characteristics in a spiral groove mechanical seal lubricated by magnetic fluid.Design/methodology/approachThe viscosity relationship of magnetic fluid in external electromagnetic field was deduced. The temperature distribution of sealing ring was calculated by the method of separation variables.FindingsIt has been found that the rotating ring absorbs most friction heat. The temperatures on the end faces of rotating ring and stationary ring decrease from inner radius to outer radius, the temperature of magnetic fluid film decreases from rotating ring to stationary ring and the highest temperature of the sealing system is at the junction of the inner radius and the end face of rotating ring.Originality/valueSelecting the sealing rings with higher thermal conductivity and reducing the volume fraction of solid particles in magnetic fluid can reduce the temperature of sealing system effectively.

Effect of Viscous Fluid on the Counter-Current Imbibition Phenomenon in Two-Phase Fluid Flow Through Heterogeneous Porous Media with Magnetic Field

In this paper, the counter-current imbibition phenomenon is discussed in a heterogeneous porous medium with the consideration of magnetic field effects due to the presence of magnetic fluid particles in injected fluids. An advanced analytical approximation method, i.e., homotopy analysis method is used to derive an expression for finding the saturation profiles with and without considering the magnetic field effect with the choices of different parameters. Simulation results are developed to study the effects of different parameters on saturation rate and on recovery rate of the reservoir.

Local arrangement of particles in magnetic fluids due to the measurement alternating field

Changes in the magnetic susceptibility spectrum of ferrofluids, χ(ω), due to the nanoparticle agglomeration are common when a static magnetic field is superimposed on the measuring field, but here we report on changes which occur in the absence of a static magnetic field, solely in the presence of the measuring field, over the frequency range of 50Hz–13MHz and irrespective of the colloidal stability of samples. The result is explained in terms of local rearrangement of particles within ferrofluids subjected to low frequency alternating magnetic field.

An optical investigation of the geometric characteristics of aggregates formed by particles of magnetic fluid

We have studied the dimensions of elements of a structure formed by particles of a colloidal solution of magnetite under the action of a magnetic field. The pattern observed in a thin layer of this fluid illuminated by a focused laser beam was characteristic of diffraction on the infinitely long dielectric cylinder that was used for determining the dimensions of separate aggregates. The obtained results proved to be well consistent with the values determined by means of optical microscopy.

Sedimentation of two non-magnetic particles in magnetic fluid

Magnetic fluid is a stable suspension of solid phase magnetic particles of diameter about 10 nm in a nonmagnetic carrier fluid like water or alcohol. Nowadays, the magnetic fluid is widely used in industry areas such as sealing, damping, lubricating, sound regulation, heat dissipation, and MHD beneficiation. Researchers have paid great attention to the behaviors of non-magnetic particles (NPs) in the magnetic field because magnetic fluid containing NPs can form different microstructures, which are easily controlled by applying a magnetic field. In order to appropriately use the properties of magnetic fluid in industry, it is necessary to study the interaction among NPs in detail. In this paper, a multi-physical numerical model is employed to investigate the sedimentation of two NPs in magnetic fluid subjected to an applied magnetic field. The magnetic fluid flow is simulated by lattice Boltzmann method, and magneto hydrodynamics is calculated with a self-correcting procedure of a Poisson equation solver, which enables the Ohm's law to satisfy its conservation law. A dipole force model is used to obtain the dipole interaction force between particles. In addition, as the permeability of the magnetic fluid is quite different from those of the NPs and magnetic fluid, correctly establishing the conjugate boundary condition of the magnetic intensity at the interface between the particles and surrounding fluid is a key because it affects the magnetic induction in the fluid-structure interaction area. A smooth transition scheme of the conjugate boundary condition for magnetic intensity at the interface between the particles and surrounding fluid is used in this work. The aim of this work is to investigate sedimentation of two NPs in magnetized magnetic fluid. By changing the ratio of magnetic permeability and the magnetic parameter, it is found that altering the ratio of magnetic permeability is more effective to change the trajectories of NPs, while changing the magnetic parameter can just give rise to a slight transform of particle trajectories. This can provide good theoretical support for the application of magnetic fluid in industry area, because the results in the present simulation can quantitatively analyze the controlling of the movement of NPs.

Behavior of both Nonmagnetic Particles and Magnetic Particles in Magnetic Compound Fluids in a Micro-Tube with Axial Flow under Rotating Magnetic Field

Behaviors of both micrometer-size nonmagnetic abrasive particles and micrometer-size magnetic particles in a magnetic fluid are investigated by using the discrete particle method which is based on the simplified Stokes dynamics. Sheet-like clusters of nonmagnetic particles and sheet-like clusters of magnetic particles alternately appear one after another in the axis direction when the flow velocity is small.

TO EVALUATION TEST OF QUALITY OF MAGNETIC FLUIDS FOR MAGNETOFLUID DEVICES

Magnetic fluid is a colloid of magnetic nanoparticles. Using of magnetic fluids in technical devices demands applying of strong non-uniform magnetic fields for a long time. One of the most widespread magnetic fluid devices are magnetic fluid seals of mobile shafts, magnetic fluid supports, bearings, acceleration and angle of inclination gauges, devices for information input in the computer and etc. These devices demand high quality of used fluids. Processes of magnetophoresis and Brownian diffusion in magnetic fluid lead to concentration of magnetic particles in the areas with higher intensity of magnetic field and increase of fluid magnetization in these areas. A local change of particles concentration in the fluid leads to variation of its physical properties. Formation of aggregates from the particles and the further stratification of magnetic fluid, up to its destruction, may be the most serious consequence of redistribution of concentration of magnetic particles. These factors lead to variation of parameters of magnetic fluid devices; cause disturbance of their normal operation and even failure. Therefore, the consistent, high quality magnetic fluids which are not subject to fast stratification in a non-uniform magnetic field are necessary for effective work of the devices. The procedure of evaluation test of quality of magnetic fluids is proposed in this paper. The test is based on studying of influence of processes of magnetophoresis and Brownian diffusion of magnetic particles in magnetic fluid on the forces acting on the volume of fluid in an external non-uniform magnetic field. The procedure is developed on the basis of analysis of magnetic force variation in time under the action of non-uniform field of permanent magnets. Methods of determination of stability of magnetic fluid, known at present, demand rather complicated equipment and laborious and complex investigations. Proposed procedure can be used as an express method for evaluation of magnetic fluid quality for usage in technical devices, and it does not need complicated equipment.

Magnetization mechanism of nonferrous wear debris by magnetic fluid in ferrography

The application of magnetic fluid in ferrography has improved the technique for separating nonferrous wear debris by magnetic means. Brass debris was used as an example to analyze the magnetization mechanism based on ferrographic experiments and molecular analysis. The results show that the nanomagnetic particles in magnetic fluid attach to the surface of the micro nonferrous debris by the functional group of surfactant molecule so as to develop in that debris a positive susceptibility and make it responsive to the magnetic field. The magnetic action of the magnetic particles is selective as to the property of the debris surface to which it attaches, and the magnetization time depends on how readily of the attachment. Mathematical derivation based on mechanical models shown that the magnetic force exerted on the debris is strong enough for its precipitating on ferrogram.

On the Fulfillment of Curie’s Law in Magnetic Fluids

A fulfillment of Curie’s law in magnetic fluids provides an option of their thermometric applications to measure thermodynamic temperature. On the other hand, it was shown elsewhere that the initial magnetic susceptibility χ of magnetic fluids follows Curie–Weiss’s law rather than Curie’s law. To obtain its values, use was made of the formula χ = М/Н0, where М is magnetization, and Н0 is the external magnetic field strength without any specimen. This work deals with investigations of the dependence of magnetic susceptibility of magnetic fluid on temperature for the cases where its values are found via the following formulas: 1) χ = М/Н0, and 2) χ = Мμ0/В, where В is the magnetic field induction inside the specimen. It is found that in the first case the temperature dependence of χ obeys Curie–Weiss’s law while in the second case – Curie’s law. The reason for this results from the fact that induction В acting on the particles of magnetic fluid is noticeably higher than that of the external field, В0.

Calculation of magnetic fluid parameters from the temperature dependence of the microwave reflection spectrum

We analyze the possibility of determining three parameters of a magnetic fluid (permittivity, volume fraction of the solid phase, and diameter of magnetic fluid particles) simultaneously from the temperature dependence of the reflection spectrum of microwave radiation. The reflected signal is detected using a microwave interferometer in a magnetic field, and the microwave interferometer is loaded with a layer of a magnetic fluid. Analysis of the spectral dependence of the reflection coefficient and its temperature dependence makes it possible to get information on the properties of the magnetic fluid under investigation, to refine the value of the permittivity of the magnetic fluid, and to obtain the effective permittivity of nanosize magnetic particles.

Three-dimensional and analytical modeling of microfluidic particle transport in magnetic fluids

We present an analytical model that can predict the three-dimensional (3D) transport of non-magnetic particles in magnetic fluids inside a microfluidic channel coupled with permanent magnets. The magnets produce a spatially non-uniform magnetic field that gives rise to a magnetic buoyancy force on the particles. Resulting 3D trajectories of the particles are obtained by (1) calculating the 3D magnetic buoyancy force exerted on the particles via an analytical distribution of magnetic fields as well as their gradients, together with a nonlinear magnetization model of the magnetic fluids, (2) deriving the 3D hydrodynamic viscous drag force on the particles with an analytical velocity profile of a low Reynolds number ferrohydrodynamic flow in the channel including “wall effect” and magnetoviscous effect of the magnetic fluids, and (3) constituting and solving the governing equations of motion for the particles using the analytical expressions of magnetic buoyancy force and hydrodynamic viscous drag force. We use such a model to study the particles’ trajectories in the channel and investigate the magnitude of their deflections at different flow rates, with different properties of magnetic fluids and different geometrical parameters of the system.

Mechanical Model of Nonmagnetic Mineral Particles in Magneto Hydrostatic Static Separation

Base on the fluid dynamics，electromagnetism，Newton’s law and some other basic theories，the paper analyses the equations of motion and Bernoulli for nonmagnetic mineral particles in magnetic fluid. And apply these theories to establish the mechanical model for the nonmagnetic mineral particles in magneto hydrostatic static separation (MHSS). In MHSS, the particles would be stressed by gravity force, magnetic buoyancy, ordinary buoyancy, etc. The wedge-shaped magnetic poles can set up the magnetic buoyancy of which direction is straight up, and the levitation force could be stronger in ferromagnetic fluid. And it can be calculated equating normal buoyant weight to the magnetic buoyant force that any nonmagnetic substance can be floated in magnetic fluid. The paper also analyses some parameters that affect the separation result, such as the magnetic field intensity and the magnetic field gradient. These tasks may give some supports for MHSS applied in industrial.