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The current investigation focuses on the magneto-nanofluid mixed convective boundary-layer flow of nanofluid caused by a vertical permeable plate with nonlinear thermal radiation. Furthermore, heat and mass transfer for water-base fluids influenced by heat generation/absorption and viscous dissipation have been analyzed. The convective boundary condition is also imposed on the vertical sheet. The main aim of the study is to investigate the five different types of nanoparticles, namely, silver $ ({\hbox{Ag}}) $ (Ag) , copper $ ({\hbox{Cu}}) $ (Cu) , alumina $ ({\hbox{A}{\hbox{l}_{\rm 2}}{\hbox{O}_{\rm 3}}})\hbox{,} $ (A l 2 O 3 ) , copper oxide $ ({\hbox{CuO}}) $ (CuO) , and titanium dioxide $ ({\hbox{Ti}{\hbox{O}_{\rm 2}}}) $ (Ti O 2 ) in the base fluid water. Moreover, the governing partial differential equations are converted into a set of ordinary differential equations via Sparrow–Quack–Boerner local nonsimilarity method. Additionally, nonlinear ODEs are successfully tackled by the Runge–Kutta–Fehlberg method. Physical parameters are examined graphically along with the velocity, temperature, and concentration distribution. Further, the skin friction coefficient, local Nusselt number, and Sherwood numbers are also studied in detail using graphs. The results show that increasing the value of buoyancy parameter and magnetic parameter fluid exhibits more resistance in the fluid, thereby fluid velocity and momentum boundary layer reduce. Moreover, the radiation parameter transmitted more heat from the surface to the fluid; as a result, the fluid temperature is boosted. [ABSTRACT FROM AUTHOR]

A novel and effective adsorbent based on magnetic polymeric ionic liquid nanocomposite-coated hollow fiber membrane (MPILNC-HFM) was developed and applied for magnetic solid phase extraction of Pb (II) and Cu (II) from environmental water and fruit juice samples with microinjection sampling-flame atomic absorption spectrometry (MIS-FAAS). During extraction process, the adsorbent coated on the surface of the hollow fiber can be removed from the solution using tweezers without using a magnet. Additionally, the need to use a centrifuge during adsorption and desorption steps is also eliminated, thereby increasing the speed, simplicity, and efficiency of the extraction process. The nanocomposite characterized through Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive x-ray (EDX) analyses to ensure its applicability. The experimental parameters were optimized by applying one-variable-at the-time (OVAT) approach. Under optimal conditions, limits of detection were achieved 16.5 µg L−1 for Pb (II) and 20.4 µg L−1 for Cu (II), respectively, with relative standard deviations up to 7.9% and relative recoveries in the range of 91.8%–02.2%. [ABSTRACT FROM AUTHOR]

This article provides a quantitative analysis of the flow of MHD micropolar fluid through a Darcian permeable medium bounded by a stretched surface. The RK45 method, along with the shooting approach, is employed to perform the analysis. The impacts of Joule heating, thermophoretic, and Brownian diffusions over the fluid flow are particularly, focused in this research work. The study's findings can be applied in nanofluid technology for optimizing heat transfer, porous media engineering for designing efficient systems, and magnetohydrodynamics for applications like magnetic drug targeting and liquid metal cooling in nuclear reactors. The nonlinear partial differential equations (PDEs) that govern the flow are altered into nonlinear ordinary differential equations (ODEs) by using appropriate variable similarity transformations. Displayed the graphical effects of various physical factors over the velocity, angular velocity, concentration, and temperature profiles. Velocity profiles are enhancing as the micropolar fluid and porous factor rises whereas the opposite trend exists for the boosting estimations of the magnetic parameter. Temperature distribution is escalating for the rising estimations of the magnetic, Eckert, Brownian, and thermophoresis parameters but there is an opposite scenario deploys as the Prandtl number upsurges. As Schmidt and Brownian motion parameters increase, the micropolar nanoparticle concentration decelerates and elevates when the thermophoresis parameter is boosted. The micro-rotation profiles are enhanced as the values of the micropolar fluid parameter rise. The drag force was enhanced as the magnetic and micropolar fluid parameters upsurged but diminished when the porous parameter was elevated. The rate of heat flow diminishes with higher estimates of the micropolar fluid parameter but improves when the magnetic and Prandtl number parameters increase. The rate of mass flux escalates for the enhanced values of thermophoresis, Brownian, Schmidt, and chemical reaction parameters. Considerable numerical outcomes have been produced and cross-referenced with the latest study, which unveiled remarkable concurrence. [ABSTRACT FROM AUTHOR]

Coprinus comatus is an edible mushroom and its fermented product possesses antioxidant activity. In this study, to further enhance the antioxidant activity and improve the reusability of the strain, calcium alginate hydrogel was used as the carrier for embedding and immobilizing Coprinus comatus. The effects of CaCl2 concentration, sodium alginate concentration, microsphere diameter, and the amount of magnetic particle on the antioxidant activity of fermented products were investigated. The results showed that the magnetic immobilized microsphere prepared by 2.50% CaCl2, 2.00% sodium alginate and 0.50% Fe3O4 had the best fermentation antioxidant activity (EC50 was 0.43 ± 0.01 mg/mL) when the diameter was 5 mm, which increased by 24.56% compared to the initial activity. Besides, the microsphere showed strong reusability, the antioxidant activity was still better than the free strain after being used five times. This study not only enhanced the antioxidant activity of Coprinus comatus fermented product through immobilization, but also provided an effective method for microbial fermentation. [ABSTRACT FROM AUTHOR]

In this work, a magnetic fluid (Fe3O4/water) moving through a square tube in a steady-state and fluctuating electromagnetic field was investigated experimentally. The relevant parameter effects are considered, including rotating direction, flux, frequency, and frequency on the heat removal ability and flow resistance. The electromagnetic field induces the particles to move to the square tube wall, greatly influencing the boundary layer disturbance. A greater electromagnetic flux and rotating direction enhance nanoparticle turbulence intensity and local thermal conductivity. Compared to when it is fixed, the Nu of an electromagnetic field oscillating at 1.25 hz, 2.3 µT, is 9.16% more. Additionally, compared to the other modes, the Nu is greater by 3.41% when the mixed mode of the electromagnetic field rotates at 1.25 hz and 0.5 µT. The heat-removal capacity may be significantly increased by increasing the electromagnetic flux and frequency, which raises the Nu. The f is also further increased by the disruption of electromagnetic flow. [ABSTRACT FROM AUTHOR]

In the present investigation, influence of the chemical reaction, magnetic field and slip on micropolar fluid flow via a porous wedge in the existence of Hall and ion-slip are examined. The pertinent highly non-linear PDEs are changed into an arrangement of non-linear coupled ODEs by utilizing similarity transformation. The equations were calculated using the 'Keller Box Method' (KBM). The numerical data for skin-friction coefficients, Nusselt number, Sherwood number, velocities, thermal and concentration fields are portrayed by graphs for various existing parameters and analyzed in detail. The heat transfer characteristics of working magnetic fluid escalated with acceleration in slip and power-law parameters. Moreover, the mass transfer function escalated with material and chemical reaction parameters. [ABSTRACT FROM AUTHOR]

The features of ferromagnetic fluids make it supportive for an extensive range of usages in directing magnetic drugs and magnetic hyperthermia. Owing to all such potential applications, the current study is concerned with the ferromagnetic liquid flow past a stretching sheet with thermophoretic particle deposition and a magnetic dipole. The equations of described flow are transformed into ordinary differential equations (ODEs) by selecting suitable similarity variables. These ODEs are later solved numerically by the fourth and fifth-order Runge–Kutta–Fehlberg (RKF-45) technique by using a shooting scheme. The influence of sundry parameters on velocity, thermophoretic diffusive deposition velocity, skin-friction, Nusselt number, Sherwood number, thermal and concentration profiles are illustrated graphically. The results reveal that the increase in ferromagnetic interaction parameter improves the thermal profile but declines the velocity and concentration profiles. The imposition of thermophoretic particle deposition results in declination of the mass transfer. The escalating values of the ferromagnetic interaction parameter decline the rate of heat transfer. Finally, the rise in values of the thermophoretic parameter and thermophoretic coefficient decays thermophoretic diffusive deposition velocity. [ABSTRACT FROM AUTHOR]

An efficient synthesis of new (methylsulfonyl)benzopyranophenazin-3-amines via the condensation of 2-hydroxynaphthoquinone, 1,2-phenylenediamine, methylsulfonylacetonitrile, and arylaldehydes derivatives catalyzed by ionic liquid [(EtO)3Si–CH2–CH2–CH2–NH3+][HCOO−] immobilized on magnetic Fe3O4@SiO2, as a novel heterogeneous nanocatalyst, was described. The novel nanocatalyst was characterized by FE-SEM, XRD, FT-IR, TGA‐DTG, and VSM techniques. The environmentally friendly protocol presented some advantages, such as a simple work-up and excellent yields. This nanocatalyst can be easily reused several times and recovered by an external magnet. The activity of the recoverable nanocatalyst remains intact even after five repeated runs. [ABSTRACT FROM AUTHOR]

AbstractThis research investigates the heat transfer dynamics of a two-dimensional, incompressible, laminar, magnetohydrodynamics, time-dependent flow of a hybrid ferromagnetic fluid with radiation and irregular heat source/sink conditions through two porous channels. The study investigates the unique capability of ferromagnetic solid nanoparticles to improve the thermal efficiency of the host fluid, with potential applications in medicine such as drug targeting, cell separation, and magnetic resonance imaging. A mathematical model is developed as a nonlinear partial differential equation (PDE), which is subsequently converted into a nonlinear ordinary differential equation (ODE) using similarity transformations. The numerical solution is obtained using the 4th-order Runge-Kutta method implemented in Mathematica software. We analyze the impact of various nondimensional factors on the numerical results, including skin friction coefficient and Nusselt number, as well as graphical results depicting the velocity and temperature profiles of the hybrid ferrofluid. Boosting the film thickness parameter (λ) improves the heat transfer rate at the bottom of the porous channel. Raising the irregular heat source/sink parameters (A* and B*) and causing opposite impacts on the heat transfer rate at the bottom porous channel. Higher the radiation (R) values, the temperature profile behaves oppositely in both porous channels. The analysis reveals that the hybrid ferrofluid exhibits a higher rate of heat transfer compared to the ferrofluid. [ABSTRACT FROM AUTHOR]

Magnetic fluid is an optical functional material which comprised of magnetic nanoparticles that are dispersed in water-base fluid or oil-base fluid. For a magnetic fluid film, when magnetic field is applied perpendicularly to the surface of film, the magnetic nanoparticles can agglomerate to columns from initial dispended state, resulting in the microstructure changes which represent the different optical characteristics of the magnetic fluid film. And this characteristic can be applied for optical sensors. So the study on microstructure of magnetic fluid is very important and necessary. In this paper, the molecular dynamic method based on both spherical magnetic nanoparticle and Rod-like magnetic nanoparticle was respectively used to simulate the microstructure of magnetic fluid. The calculating results showed that for spherical computation model, the magnetic nanoparticles could agglomerate to form chains along the direction of magnetic field, as for Rod-like computation model, however, not only the process of chaining but also its periodic structure can be reflected. Finally, the reason for the difference was discussed. [ABSTRACT FROM AUTHOR]

Magnetorheological fluids (MRF) are regarded as a novel 'intelligent' material because they show the ability to respond to external stimuli. However, with the extension of working time, the agglomeration and sedimentation of magnetic particles become a serious problem, which has a great impact on the magnetorheological performance. Many methods have been proposed to overcome the particle settling problem, including magnetic particle modification and carrier liquid modification, but they all show negative effects on the magnetorheological performance of MRF. A new method to prepare the magnetic liquid crystal (LC) composites [PEA-COOH]SO3H@Fe3O4 series, with Fe3O4 nanoparticles as core and side-chain supramolecular LC polymers with different mesogen contents as coating, were reported. The chemical structure, magnetic property and LC properties were investigated by a variety of techniques. In order to study the effects of the mesogen content and LC phase state of magnetic LC composites on magnetorheological performance and sedimentation stability, MRF based on silicone oil carrier liquid and [PEA-COOH]SO3H@Fe3O4 dispersed phase were prepared. It was found that dynamic yield stress, plastic viscosity and the sedimentation ratio increased slightly with increasing mesogen content in the magnetic LC composites. What's more, MRF prepared by magnetic LC composites annealed in LC state exhibited better magnetorheological performance and sedimentation stability than those in glassy state and isotropic state. These results indicated that the synergetic effects of LC orientation and magnetic field-induced arrangement of Fe3O4 magnetic particles can improve the magnetorheological performance and sedimentation stability of MRF. [ABSTRACT FROM AUTHOR]

A simple and green hydrophobic magnetic ionic-liquid assisted dispersive liquid-liquid microextraction (MIL-DLLME) was optimized for the determination of trace cadmium (Cd (II)) in environmental and food samples by flame atomic absorption spectrophotometer. To achieve selective and sensitive extraction of Cd (II), four MILs were prepared and tested. Extraction parameters of the MIL-DLLME including pH, type and volume of the MIL, type and volume of dispersive solvent, extraction cycle, ionic strength and sample volume were investigated in detail and optimized by Box–Behnken design. Under optimum conditions, matrix effect, recovery study, intra-day and inter-day precision were performed for the MIL-DLLM. The analytical characteristics such as limit of detection, limit of quantification and pre-concentration factor were 0.17, 0.56 and 125 ng mL−1, respectively. The validation of the MIL-DLLME was evaluated by analysis of reference materials. Moreover, the accuracy of the results in the analysis of real samples was evaluated by standard addition and quantitative recoveries (91 ± 5–101 ± 2%) were achieved. The results obtained in the analysis of both reference materials and real samples showed that the MIL-DLLME has a selective applicability for cadmium. [ABSTRACT FROM AUTHOR]

Ferrofluids containing polydisperse magnetic nanoparticles are made stable using surfactant(s) in a compatible dispersion medium. The commercial ferrofluid APG 513 A (Ferrotec Corp) has demonstrated irreproducibility in the magneto-viscous (MV) effect from different batches. The MV effect changes from about 414% to 50% in studies from 2002–2015. This change was attributed to the removal of large Brownian particles, agglomerates and clusters resulting from dipole-dipole interactions. Even after the removal of these clusters, some residual MV effect was noted which was attributed to the preexisting aggregates produced during the fluid manufacturing process. The new APG 513 A was investigated to clarify the issue of the batch to batch irreproducibility and the existence of pre-aggregates in the fluid. The viscosity with and without a magnetic field along with magneto-granulometric, dynamic light scattering, TEM and FTIR were studied to qualify the new sample. This new APG 513 A had shown a very low MV effect (∼ 20%). The large Brownian particles were responsible for the effect and there was no evidence of dipolar interactions. The issue of preexisting aggregates was resolved by systematically diluting the fluid with the carrier. Above measurements along with the zero-field-cooled (ZFC) magnetization behavior which has never been reported in the literature before were studied on the diluted samples. The data analysis with the existing models confirms that the present APG 513 A is composed of individually stabilized particles including Brownian particles with a long sheath of dual surfactant, absence of preexisting aggregates, no evidence of dipolar interactions and a narrow size distribution. [ABSTRACT FROM AUTHOR]

Considering the Navier Stokes equations paired with the heat equation for ferrohydrodynamic flow of magnetic nanofluid amidst two rotating porous disks, nothing is known on the significance of geothermal viscosity for the magnetic fluid flow between co-rotating porous surfaces. The current analysis considers the effects of changing viscosity and thermal radiation. Additionally, the stretching and angular velocities of the two disks differ. The flow model's estimated basic equations are transformed into nondimensional ordinary differential equations (ODEs) with the proper transformation before being numerically solved using Maple's built-in BVP Midrich approach. For velocity and temperature fields, the effects of active flow parameters such as the depth-dependent viscosity variation parameter, ferro-hydrodynamics interaction parameter, Reynolds number, Prandtl number, Darcy number, Eckert number, and radiation parameter are discussed. It is worth noticing that the temperature field tends to decline as the Darcy parameter is higher estimated. It is worth concluding that there exists a high fluctuating viscosity around the lower disk, the magnitude of horizontal velocity decreased, but vertical velocity increased everywhere else. Furthermore, skin friction becomes more valuable at higher Reynolds numbers and porosity estimates. [ABSTRACT FROM AUTHOR]

Development of a two-phase incompressible solver for magnetic flows in the magnetostatic case is presented. The proposed numerical toolkit couples the Navier–Stokes equations of hydrodynamics with Maxwell's equations of electromagnetism to model the behaviour of magnetic flows in the presence of a magnetic field. To this end, a rigorous implementation of a second-order two-phase solver for incompressible nonmagnetic flows is introduced first. This solver is implemented in the finite-difference framework, where a fifth-order conservative level set method is employed to capture the evolution of the interface, along with an incompressible solver based on the projection scheme to model the fluids. The solver demonstrates excellent performance even with high density ratios across the interface (Atwood number $ \approx 1 $ ≈ 1), while effectively preserving the mass conservation property. Subsequently, the numerical discretisation of Maxwell's equations under the magnetostatic assumption is described in detail, utilising the vector potential formulation. The primary second-order solver for two-phase flows is extended to the case of magnetic flows, by incorporating the Lorentz force into the momentum equation, accounting for high magnetic permeability ratios across the interface. The implemented solver is then utilised for examining the deformation of ferrofluid droplets in both quiescent and shear flow regimes across various susceptibility values of the droplets. The results suggest that increasing the susceptibility value of the ferrofluid droplet can affect its deformation and rotation in low capillary regimes. In higher capillary flows, increasing the magnetic permeability jump across the interface can further lead to droplet breakup as well. The effect of this property is also investigated for the Rayleigh–Taylor instability growth in magnetic fluids. [ABSTRACT FROM AUTHOR]

In this work, the three-dimensional unsteady flow was scrutinized adjacent to a flat plate immersed inside a fluid with electric conductivity in the presence of constant magnetic field. An extended model of group transformation method was exploited, comprising three parameters, to transform the mathematical model into a new system of ordinary differential equations (ODEs). The proposed method is rarely and seldom used in handling higher dimensions coupled equations. Two cases were studied, the stretching and shrinking plate. In the first case, the results showed that both of magnetic parameter, M, and Prandtl number, Pr, affected inversely the fluid velocity, the shear stress and the temperature distribution. On the contrary, the heat flux increased when both M and Pr increase. That could be interpreted by the effect of larger magnetic force and fluid viscosity, respectively. In case of shrinking plate, the attained results were opposite to those of stretching case specially for the effect of magnetic parameter. [ABSTRACT FROM AUTHOR]

Magnetic fluid sealing (MFS) is one of the most advanced applications of magnetic fluids (MF). To improve the pressure resistance of the traditional MFS with a large gap, this paper proposes a large-gap divergent embedded magnetic fluid seal (DEMFS) structure with radial and axial sealing capabilities. Through the simulation analysis of the radial and axial seal gaps (0.5–0.8 mm) and the number of radial and axial pole teeth (PT), the theoretical pressure resistance was obtained. A large-gap DEMFS test bench was built to experimentally verify the simulation results, and the effects of the MF volume and shaft speed on the pressure resistance of the sealing device were also experimentally investigated and compared with the theoretical pressure resistance of the traditional MFS structure. The numerical simulation and experimental results that the experimental values of the DEMFS are in good agreement with the theoretical values. When the MF injection volume was 2.5 ml, the pressure resistance reached the maximum and tended to be stable. With the change in the size of the seal gap and the number of PT, the variation trend of the pressure resistance of the DEMFS was different from that of the traditional MFS. When the shaft speed was low, the low speed had almost no effect on the pressure resistance of the DEMFS. The axial seal gap and axial PT were beneficial to the sealing effect. [ABSTRACT FROM AUTHOR]

An investigative approach on study of a laminar natural heat convection on different geometric annuluses under impact of a constant magnetic field, using Ferro-Nano has been carried out. The three different cases of vertical cylindrical, cubic, and twisted cubic geometries, each are presented by a 3D model. These geometries are affected by a magnetic field which affects the variables such as heat transfer, natural heat convection, and entropy generation will be investigated. The chosen approach for this article is a numerical calculation, including Energy equations, Electrical potential equation, Hartmann number, Rayleigh, and Nusselt number. Results gathered by current study indicate that magnetic field is the primary reason of natural convection reduction phenomenon on each of the presented geometries. In the end it was illustrated that the average heat transfer has been reduced to 0.6% when the magnetic field is applied. Moreover, on the subject of the geometry amends, the twisted cubic had the highest amount or reduction of all the considered cases. [ABSTRACT FROM AUTHOR]

The present investigation shows the viscosity and thermal conductivity of Mg2+ substituted nickel ferrite based magnetic fluids of different chemical compositions (Ni1-xMgxFe2O4). The nanoparticles were synthesized using a simple and cost-effective co-precipitation method. The XRD result shows the formation of a cubic spinel structure. SEM analysis confirmed the size of the nanoparticles ranges between 1 mm and 500 nm. The Experimental results show that the viscosity of magnetic fluids of two different volume fractions decreases for the rise in temperature and for the increase in rotations per minute (RPM). The results on thermal conductivity of two different volume fractions of Ni1-xMgxFe2O4 based magnetic fluids exhibit enhanced thermal conductivity than the carrier fluid (transformer oil). The thermal conductivity results were compared with Maxwell's theoretical prediction and experimental models for confirmation. [ABSTRACT FROM AUTHOR]

The settlement characteristics of magnetite particles are one of the key factors affecting the separation performance of column magnetic separator. This paper reports on the settlement characteristics of different magnetite particles under the action of complex force field measured by using a particle settlement device with an applied magnetic field. The results show that under the combined effect of fluid drag force and magnetic field, the differences in magnetite particle density and particle size are reduced, the differences in magnetic properties are amplified, and particles with different magnetic properties are separated. Based on these results, a three-product magnetic-separation column with mutually independent magnetic and fluid field structures for different magnetic particles was developed. Using this separator, the TFe grade and recovery of the concentrate were 67.93% and 92.9%, respectively. The results show that the equipment is effective in separating the liberated magnetite and other interlocking particles, thereby improving the sorting efficiency. This provides a theoretical basis for the development of column magnetic separation equipment and the improvement of magnetic separation accuracy. [ABSTRACT FROM AUTHOR]

The relationship between the magnetic susceptibility and degree of polymerization of liquid polydimethylsiloxane (PDMS) was studied experimentally. The magnetic susceptibility of the liquid PDMS was established with the Moses effect, i.e., study of the shape of the near-surface well (the well created near the surface-vapor interface) created in the liquid by a permanent magnetic field. The study of the shape of the near-surface well was carried out under experimental registration of the laser beam reflected from the PDMS/air interface. The broad range of available molecular weights of PDMS made it suitable for the study. The diamagnetic susceptibility, χ , of PDMS was measured for a broad range of molecular weights. The plot of magnetic susceptibility, χ, against the number of repeating units in the chain, n, was linear. The result was compared with the magnetic susceptibility predicted by the Pascal law. The volume magnetic susceptibility χ v of the liquid PDMS was established as χ v = (−7.77 ± 0.06) · 10−6. The magnetic susceptibility of the PDMS monomer was established as χexp(n = 1) = (60.3 ± 0.32) · 10−11, which is in a satisfactory agreement with the Pascal empirical rule. [ABSTRACT FROM AUTHOR]

Small-angle neutron scattering (SANS) is widely used in structural analysis of complex liquid dispersions. An essential feature of SANS experiments for such systems is hydrogen/deuterium isotopic substitution in liquid media, which makes it possible to change the neutron scattering length density of the solvents, thus providing the basis for the contrast variation technique. In some cases, for dispersed particles with near-spherical symmetry, one can observe in the scattering curves specific points at which the scattered intensity is independent of the scattering contrast between dispersed particles and solvent. These points are referred to as 'isoscattering points' and in monodisperse solutions related to the particle size. Here, we report this effect for rather polydisperse (above 40%) magnetic fluids with core-shell particles in a liquid medium (water). It is shown that the effective isoscattering point can be analyzed to some extent for polydisperse systems, which gives additional possibilities for structural characterization of complex solutions via SANS. [ABSTRACT FROM AUTHOR]

The stability of a stabilized with polydimethylsiloxane (PDMS) magnetic fluid to alcohols of a saturated homologous series was investigated. We used alcohols with a linear molecular structure and their possible isomers. It was found that the solubility of the PDMS stabilized particles strongly depends on the molecular weight of the coagulant and, quite unexpectedly, on the degree of isomerization. The first tested coagulants, ethanol and acetone, did not mix with PDMS stabilized magnetic fluid. The next member of the homologous series, linear propanol, is the most effective coagulant that causes a sharp precipitation of particles. Meanwhile, with isopropanol, coagulation occurs very smoothly. The butanol isomers differ even more. Normal butanol causes the liquid to coagulate at a higher concentration than propanol, whereas tret-butanol mixes with PDMS stabilized magnetic fluid in any proportion. The last linear alcohol in the homologous series that can serve as a coagulant is hexanol-1. The next members of the homologous series do not mix with the PDMS stabilized magnetic fluid. This is typical only for linear molecules. For example, 2-ethylhexanol (isooctanol) perfectly dissolves PDMS stabilized particles. This property can be used to separate mixtures of isomers and linear molecules. [ABSTRACT FROM AUTHOR]

This paper studies the influencing factors on the magnetic material (nickel-phosphorus coated SKD11 steel) polishing process were determined by investigating the distribution of magnetic iron (MIGs) and abrasive grains (AGs) in the working surface of magnetic liquid slurry (MLS). The influence of the factors, namely the diameters of the MIGs and the AGs and working distance (K), on the polishing surface quality was assessed by fuzzy gray analysis. Results showed that the values of the fuzzy gray relationships with the factors were 0.6361, 0.5181, 0.8804, and 0.6464. Result showed that the fuzzy gray relationship point of factors known as K exerted the most remarkable influence on the polishing effect, whereas the effect of MIG diameter was insignificant. The experimental results indicated that MLS containing MIGs with a diameter of 5 μm, AGs with a diameter of 1.5 μm and K = 1 mm should be prepared to create a mirror surface with nickel–phosphorus coated SKD11 steel. An extremely smooth mirror surface with Ra = 0.926 nm is produced under these experimental conditions, leaving no scratches and impurities on the machined surface. The proposed polishing method that uses MLS with MIGs and AGs (which are low-cost and commercially available) is suitable and effective for polishing the surface of magnetic materials with extremely high accuracy. [ABSTRACT FROM AUTHOR]

Although the sealing mechanism of the embedded magnetic fluid seal is unclear, it is an effective way to improve the performance of the ordinary magnetic fluid seal. Embedded magnetic seals can be divided into diverging and converging embedded magnetic fluid seals, according to the direction of leakage of the sealed medium. This article mainly focuses on presenting a sealing device that can observe the change in the shape of the magnetic fluid film and investigate the mechanism of diverging and converging embedded magnetic fluid seals. The pressure transfer mechanism of the embedded magnetic fluid seal with a large gap was studied through experiments. Numerical analysis of the magnetic field distribution in the seal gap and calculation of the theoretical pressure capacity of the embedded magnetic fluid seal are produced on the basis of embedded magnetic fluid seal theory. The experimental pressure capacity is compared with the theoretical pressure capacity to verify the correctness of the embedded magnetic fluid seal pressure capacity theory. The research has investigated the effect of the number of magnetic fluid film ruptures on the self-restoring capacity of embedded magnetic fluid seals, compared with the self-restoring capacity of diverging and converging embedded magnetic fluid seals, and analyzed the data. The results illustrated that the experimental pressure capacity of the embedded magnetic fluid seal matched well with the theoretical pressure capacity, which verifies the correctness of the embedded magnetic fluid seal theory. The pressure transfers from one chamber to another when the pressure difference between the two sides of the magnetic fluid film under the pole tooth is larger than the pressure capacity of the magnetic fluid seal, and the air will enter from the high-pressure side seal chamber to the low-pressure side seal chamber, in turn. As the inlet pressure increases, the pressure trend in the radial chamber of the embedded magnetic fluid seal differs from that in the axial chamber. When the seal fails, the magnetic fluid shows microleakage and complete leakage. As the number of magnetic fluid film ruptures increases, the self-restoring capacity first decreases and then increases. The self-restoring capacity of the converging embedded magnetic fluid seals is better than that of the diverging embedded magnetic fluid seals. [ABSTRACT FROM AUTHOR]

A magnetorheological fluid (MRF) is a smart composite suspension composed of nonmagnetic liquid and soft magnetic particles. Carrier fluids can considerably influence the performance of MRFs; therefore, to investigate the effect of carrier fluids on MRFs, an SO/IL-MRF was prepared by mixing an ionic liquid (IL) with silicone oil (SO) in this study. Three types of MRF samples were prepared for experiments (pure SO, pure IL, and SO/IL). According to the experimental results, the SO/IL-MRF has better sedimentation stability than those based on pure SO and pure IL. Further, three methods were used to determine the shear yield stresses of the MRFs. The SO/IL-MRF achieved a higher shear yield stress than those of the other two because a network structure is formed between the ionic fragments and the molecular chains of the SO in the SO/IL-MRF. This increases the movement resistance of the particles in the carrier fluid, and it is unlike the mechanism of the IL-enhanced MRF. This work provides new ideas for improving the MRF performance. [ABSTRACT FROM AUTHOR]

In this paper, we consider the global regularity of 2D magnetic Bénard fluid equations with almost magnetic diffusion and thermal diffusivity and without kinematic viscosity. We focus on this goal in two ways. In one way, the magnetic diffusion and thermal diffusivity are separately given by D 2 and D 3 two Fourier multipliers whose symbols m 2 and m 3 are respectively given by m 2 (ξ) ≡ | ξ | 2 log ⁡ (e + | ξ | 2) β and m 3 (ξ) ≡ | ξ | 2 log ⁡ (e + | ξ | 2) γ . In another way, we generalize the previous case and the magnetic diffusion and thermal diffusivity are separately given by L 2 and L 3 two Fourier multipliers whose symbols m 2 and m 3 are respectively given by m 2 = | ξ | 2 g 2 (ξ) and m 3 = | ξ | 2 g 3 (ξ) , where g j = g j (| ξ |) (j = 2 , 3) are two radial non-decreasing smooth functions. [ABSTRACT FROM AUTHOR]

We developed a sound absorber using a magnetorheological fluid(MR-F) based on the density and alignment angle of carbonyl iron powder(CIP) chains by the controlling the magnetic field strength and direction. The magnetically arranged CIP lattice structure considerably influenced the sound transmission loss(STL). We used optical microscopy, energy-dispersive X-ray spectrometry, and X-ray diffraction to investigate the STL by varying the magnetic field strength from 0 to 40 mT and the angle from 0 to 30°. The STL was markedly increased (133%) owing to an ∼10-fold increased density and the CIP alignment. These results were verified using the developed MR-F porous model. Sound transmission loss was significantly increased by sound insulation effect of a magnetorheological fluid as a function of magnetic field strength and direction. [ABSTRACT FROM AUTHOR]

In this study, dynamic modeling of an elbow axially functionally graded (AFG) macro/micro-tube carrying magnetic flow with different cross-sections is considered. Parametric optimization is performed for vibration suppression of such fluid-interaction systems. Implementing computer simulations, passive vibration control procedures, along with the effect of AFG materials and magnetic properties of the fluid as well as precisely manufactured geometry of the system, is investigated. It is assumed that the material characteristics of the system vary in the longitudinal direction based on exponential and power-law distribution profiles. Influence of the downstream inclination angle and cross-section area on the stability of the system is studied. The governing dynamical equation of the system is derived. Fundamental frequency and critical fluid velocity of the system are obtained. It is demonstrated that both circular cross-section area configuration and an increase in elbow inclination angle result in system stability enhancement. It is also shown that AFG materials can significantly enhance the fundamental frequency and stability threshold of the system in comparison with uniform materials. Undoubtedly, modeling and proposed control approaches can facilitate the design of macro/microstructures transporting fluid. [ABSTRACT FROM AUTHOR]

A polarization beam splitter (PBS) based on a magnetic fluid-filled dual-core photonic crystal fiber is characterized. This is the first time that anisotropy of magnetic fluid is applied to the fiber polarization beam splitter. The designed device is able to separate x and y polarization modes completely by applying an external magnetic field. When the length of the device is 9.905 mm (or 16.795 mm), the maximum bandwidth of the effective working wavelength is 26 nm (or 70 nm) and the tunable magnetic field width is approximately 5 Oe (or 165 Oe) corresponding to magnetic field range from 24 to 29 Oe (or 135 to 300 Oe). By tuning the external magnetic field, the proposed beam splitter may be selected to operate in the S, C, and L bands, and the working wavelength bandwidth and center wavelength are tunable. [ABSTRACT FROM AUTHOR]

The magnetically assisted resistance spot welding (MA-RSW) method provides a promising approach for improving weld performance. However, the MA-RSW process involves complex multiphysics fields that make numerical modeling very challenging. Thus, most resistance spot welding (RSW) models adopt electrothermal-mechanical coupling and ignore the influence of fluid flows caused by electromagnetic forces on nugget growth. In this paper, a magnetohydrodynamic (MHD) model, which couples the electric, thermal, magnetic and flow fields, is developed to explore the influencing mechanism of an external magnetic field (EMF) on the flow patterns and microstructures of aluminum resistance spot welds. Numerical results show that the application of an EMF can lead to the formation of Lorentz force in the liquid nugget, which transforms the flow pattern from an in-plane flow to a combined in-plane and out-of-plane flow. The flow velocity of molten metal in the MA-RSW process is 5 times higher than that of the RSW process, and the maximum temperature of the MA-RSW model is reduced from 774°C in the MHD RSW model to 725°C. Therefore, the MA-RSW joint exhibits a 25.5% larger nugget diameter, a more than 20% finer grain structure, and fewer defects than the RSW joint in the experimental results. [ABSTRACT FROM AUTHOR]

Although liquid crystal elastomers (LCE) are a fascinating class of materials with interesting thermomechanical properties of their own, the aim is to enhance their performance or add new features, e.g. response to external stimuli. The generally weak response of organic materials can be significantly intensified by mixing nano-sized magnetic particles into the host polymer matrix. An alternative approach is chemically coupling the nanoparticles to the elastomer. We achieved this by bonding functionalised magnetic nanoplatelets to the backbone of a main-chain LCE and obtained polydomain magnetic liquid crystal elastomers. We measured the magnetisation curves in samples, which were exposed to either small or large magnetic fields – their response being a consequence of partial particle reorientation or magnetic moment flipping. In contrast to the samples, which were exposed to small magnetic field and in which the remanent magnetisation can be reset to zero by heating the sample, the samples with flipped magnetisation within the platelets cannot be reversed into the original state. Coupling of magnetic and mechanical properties shows a slight magneto-elastic response at elevated temperatures and a significant inverse magneto-elastic effect: the magnetisation caused by mechanical stretching is almost equal to the magnetisation caused by an external magnetic field. [ABSTRACT FROM AUTHOR]

Instability modes of viscoelastic Taylor–Couette flow in the Keplerian regime are investigated using both linear stability analysis and experimental detection of critical states. A generalised Rayleigh criterion has been derived and it allows to separate the zone of potential purely elastic instability modes and the zone of stability. The analogy between the instability of viscoelastic Taylor–Couette flow in the Keplerian regime and the magnetorotational instability (MRI) of conducting magnetic fluids is established. Viscoelastic stress tensor can be represented by a tensor product of magnetic-like vectors. This allows to use the Velikhov-Chandrasekhar criterion of the MRI to predict the elasto-rotational instability (ERI). ERI modes obtained in linear stability and in the experiments are assumed to represent the MRI analogue modes as they are observed in the stable zone according to generalised Rayleigh discriminant. [ABSTRACT FROM AUTHOR]

We present an experimental study on terahertz (THz) magneto-optical (MO) properties of tri-layer graphene on quartz substrate, grown by chemical vapor deposition. The MO conductivities are measured in the Faraday geometry by applying optical polarization and using THz time domain spectroscopy (TDS) in high magnetic fields at liquid nitrogen temperature. We find that the real and imaginary parts of the longitudinal and transverse MO conductivities fit well to the classic MO Drude formula for tri-layer graphene. Thus, we are able to determine optically the key sample parameters such as the electron density, the electron effective mass and the relaxation time for tri-layer graphene. The dependence of the relaxation time on magnetic field is examined. This work indicates that THz TDS can be employed as a powerful tool to measure MO properties of tri-layer graphene and other 2D electronic materials in the presence of high magnetic fields. [ABSTRACT FROM AUTHOR]

Most magnetic fluid seals are multitooth structures for the high sealing capacity. However, the pressure transfer mechanism in the multitooth magnetic fluid seal is only carried out through experimental methods. In this article, a simulation method is presented to solve the two-phase flow of magnetic fluid and air in the sealing clearance. The boundary of the magnetic fluid is obtained by a volume of fluid method. In addition, a planar multitooth magnetic fluid seal is presented to observe the magnetic fluid barrier and obtain the pressure change during the pressure transfer process. The result shows that the fluid barrier ruptures when the pressure difference exceeds the sealing capacity. The pressure is transferred chamber by chamber in the multitooth magnetic fluid seal. [ABSTRACT FROM AUTHOR]

Magnetic fluid heating has great potential in the fields of thermal medicine and cryopreservation. However, variations among experimental parameters, analysis methods and experimental uncertainty make quantitative comparisons of results among laboratories difficult. Herein, we focus on the impact of calculating the specific absorption rate (SAR) using Time-Rise and Box-Lucas fitting. Time-Rise assumes adiabatic conditions, which is experimentally unachievable, but can be reasonably assumed (quasi-adiabatic) only for specific and limited evaluation times when heat loss is negligible compared to measured heating rate. Box-Lucas, on the other hand, accounts for heat losses but requires longer heating. Through retrospective analysis of data obtained from two laboratories, we demonstrate measurement time is a critical parameter to consider when calculating SAR. Volumetric SAR were calculated using the two methods and compared across multiple iron-oxide nanoparticles. We observed the lowest volumetric SAR variation from both fitting methods between 1–10 W/mL, indicating an ideal SAR range for heating measurements. Furthermore, our analysis demonstrates that poorly chosen fitting method can generate reproducible but inaccurate SAR. We provide recommendations to select measurement time for data analysis with either Modified Time-Rise or Box-Lucas method, and suggestions to enhance experimental precision and accuracy when conducting heating experiments. [ABSTRACT FROM AUTHOR]

A tryptophan ionic liquid (TrpIL) decorated magnetic graphene oxide (Fe3O4@SiO2-GO-TrpIL) nanocomposite has been prepared for magnetic solid-phase extraction of Sudan I–IV before their high performance liquid chromatography (HPLC) analysis. Fe3O4@SiO2 nanoparticles loaded on graphene oxide endow the as-prepared nanocomposite with superparamagnetic performance, benefiting conveniently magnetic separation of the Sudan-absorbed nanocomposites from an aqueous phase. Both TrpIL and grapheme oxide make the Fe3O4@SiO2-GO-TrpIL adsorbent possess high affinity and extraction efficiency toward target analytes, Taking full advantages of the adsorbent, each of Sudan I–IV could be accurately quantified in a linear range of 0.01–0.50 µg mL−1 with the detection limit of 1.0 ng mL−1 under the optimized conditions. A 10-fold enrichment factor was obtained. The present method was employed for the simultaneous determination of Sudan I–IV in chill and water samples with satisfactory results. The thermodynamic and kinetic investigations proved that the targets might be chemisorbed onto the Fe3O4@SiO2-GO-TrpIL nanocomposite. [ABSTRACT FROM AUTHOR]

Specifically, this work aims to achieve a power splitter and polarization separator of a guided light, basing on magnetic properties such as gyrotropy, mode coupling and optimization of geometric parameters of a magneto-photonic fiber. This fiber which makes it possible to split and separate the polarizations is characterized by the opto-geometric optimization of an Y junction based on magnetic fluid in a silicon dioxide photonic crystal fiber, able to separate combination of two guided modes TE/TM, into two waves of the same amplitude and in phase between them, an incoming light wave which arrives at the Y-branch input of the fiber. [ABSTRACT FROM AUTHOR]

The purpose of this study was to design a tribotester that can evaluate the lubrication performance of ferrofluids under the effect of a magnetic field. A novel bronze-based tribopair was fabricated with the potential to employ a controllable magnetic field in such a way that it accurately mimics the friction of a thrust pad bearing. The designed experimental scheme enables direct measurement of the normal load and the friction torque of ferrofluid-lubricated contacts. The stability of the tribotester was ensured by calibration tests. After calibration of the tribotester, lubrication tests were carried out. The surface morphology of the rubbed specimens was characterized by scanning electron microscopy, energy-dispersive spectroscopy, and optical microscopy. The friction-reducing property, antiwear mechanism, and self-repairing ability of ferrofluid lubrication are discussed according to the test and characterization results. The results show that the ferrofluid lubrication method is an effective approach for lubrication of a thrust pad bearing. [ABSTRACT FROM AUTHOR]

In the present study, we propose a new thermal conductivity model for ferrofluids using the aggregation structure of magnetic nanoparticles under external magnetic field. According to this model, in the presence of an external magnetic field, the total ferrofluid volume consists of two parts: a volume with aggregated magnetic nanoparticles - chainlike clusters and a volume with non-aggregated uniformly dispersed nanoparticles. It has been shown that with increasing the external magnetic field the degree of aggregation increases proportionally to the magnetic field strength. It has been proven that the thermal conductivity of ferrofluids along the magnetic field direction is higher than in the perpendicular direction, due to the increased contribution of aggregated magnetic nanoparticles with a magnetic field. The predictions of the proposed model of anisotropic thermal conductivity for ferrofluids were compared with the available experimental data and a good correlation was achieved. [ABSTRACT FROM AUTHOR]

We study the Cauchy problem for the 2 1 2 D incompressible magnetic Bénard fluid system with partial viscosity and derive some blow-up criteria of smooth solutions. More precisely, we first obtain a blow-up criterion of smooth solutions to the 2 1 2 D magnetic Bénard fluid system without zero magnetic diffusion and thermal diffusivity. Furthermore, we derive two blow-up criteria of smooth solutions to the 2 1 2 D magnetic Bénard fluid system without dissipation. [ABSTRACT FROM AUTHOR]

In a planar dielectric waveguide, weak confinement of a propagating mode in a high index core leads to a measurable evanescent interaction with the cladding. In this work, we study the effect of a reorientable anisotropic cladding on the behaviour of Transverse Electric (TE) and Transverse Magnetic (TM) mode polarisations using a liquid crystal (LC)-clad waveguide architecture. The polarised evanescent field of a guided mode interacts with a voltage-tunable birefringent LC cladding to deflect an out-coupled beam. Experimental measurements are coupled with a theoretical framework and show good consistency with simulation results. We isolate the effect of mode confinement by changing the thickness of the high index core. Interactions between the LC index ellipsoid and the mode polarisation are probed by changing the initial alignment of the LC. Finally, we examine the difference in deflection between TE and TM modes, which incorporates both a change in mode confinement and a difference in LC index components. [ABSTRACT FROM AUTHOR]

We study a nanocomposite consisting of a ferroelectric liquid crystal and a magnetic nanoparticle in order to explore the possibility of using it as a magnetic resonant imaging contrast agent which will measure a field of 20 V/m. To achieve this we use the ferroic properties exhibited by the nanocomposite. We used the ferroelectric liquid crystal 2-(4-((2-fluorooctyl)oxy)phenyl)-5-(octyloxy)pyrimidine mixed with FeCo nanoparticles nominally 2–3 nm in diameter in concentrations of 0.56, 4.3 and 10.8 wt%. The 10.8 wt% sample was chosen for our study because the nanoparticles acted as a lubricant for the ferroelectric liquid crystal. This concentration yields nanoparticle clusters in about 5 − 10 μm diameter spherulites. An electric field as low as 5V/cm is enough to turn and realign the spherulites where the particles are contained. We estimate the value of the magnetic in a spehrulite and associate it to the number of spherulites aligned as a function of electric field. We find thus that we can achieve low electric fields. [ABSTRACT FROM AUTHOR]

An acid-functionalized magnetic ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate, [AcMIm]-FeCl4 has been utilized for the synthesis of a series of novel highly functionalized coumarinyl-pyrido[2,3-d]pyrimidine-2,4-dione derivatives (3a–3l) by the reactions of various 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehydes (1) with functionalized aryl, 6-aminouracils. The major significant of the present procedure is the use of task-specific acidic ionic liquid which act as catalyst as well as reaction medium and thus avoiding use of organic solvent and/or protic acid catalyst. The other major advantages of the protocol are (i) shorter reaction time (1 h), (ii) easy work up procedure, (iii) excellent yields of products (91–94%), and (iv) recyclability of catalyst. The compounds (3a–3l) were identified using FT-IR, 1H NMR, and 13C NMR and mass spectroscopic studies. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the structural, magnetic, and antibacterial activities of CrxFe3−xO4 ferrofluids. CrxFe3−xO4 nanoparticles were synthesized from iron sand by a co-precipitation method using Cr3+ ion variants (x content) of 0, 0.05, 0.1, 0.15, and 0.2. The prepared nanoparticles were then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Fourier transform infrared (FTIR). The results of XRD analysis showed that the addition of Cr+ ions caused a shift in the diffraction peak, indicating the successful penetration of Cr+ ions into the Fe3O4 octahedral atomic site. The average particle size of Fe3O4 nanoparticles determined by TEM morphology analysis was 13.7 nm. In addition, the magnetic properties of CrxFe3−xO4 ferrofluids analyzed via VSM showed that the saturation magnetization ranged between 6.95 and 42.71 emu/g, while the magnetic moments were in the range of 7.47 × 10−19–19.76 × 10−19 J/T, which varied with the addition of Cr3+ ions. Furthermore, an analysis of the antibacterial activities of CrxFe3−xO4 ferrofluids revealed that bacterial viability decreased with increase in the number of Cr3+ ions. Thus, the CrxFe3−xO4 ferrofluids prepared from iron sand are potentially excellent antibacterial agents. [ABSTRACT FROM AUTHOR]

In this study, the effect of the channel dimensions on the performance of a marine MHD thruster is investigated using a fully three-dimensional numerical model. In this model, all electric, magnetic and fluid flow fields are considered in three dimensions. In addition, a simple analytical model is developed for comparison purpose and an optimisation method is proposed for the channel design to achieve the maximum efficiency and power density. The results show that at a specific output power and flow rate, the channel dimensions can be optimised to achieve the maximum efficiency or output power density, but not both. [ABSTRACT FROM AUTHOR]

Magnetic fluid is a novel magnetic functional material. The magneto-optical properties are displayed due to the tunability. In the paper, the material characterization was studied theoretically and experimentally. In the simulation, a rod-like magnetic nanoparticle model was used to simulate the motion of the magnetic particles. In the experiment, an experimental setup was designed to observe the change of the microstructure. The results showed that the magnetic particles can be aggregated to form several magnetic chains when the applied magnetic field exceeded 100 Oe. The novel magneto-optical device exhibits advantages of low cost, small size, and easy formation. [ABSTRACT FROM AUTHOR]

Magnetic fluid (MF) seals have typically been used under various vacuum and gaseous low-pressure conditions. However, there are only a few cases in which MF seals can be used in a liquid environment. To promote this concept, a series of experimental tests was run in order to study the loading process among MF seals, as well as their self-repairing performance in aqueous environments. Exploring these factors has extended our knowledge of the sealing mechanisms in liquid environments. The results show that MF seals have enhanced self-repairing abilities in aqueous environments. [ABSTRACT FROM AUTHOR]

The paper is related to the use of magnetic nanofluids (ferrofluids) in a direct absorption solar parabolic trough collector, which enhances thermal efficiency compared to conventional solar collectors. By applying the right magnetic intensity and magnetic field direction, the thermal conductivity of the fluid increased higher than typical nanofluids. Moreover, the ferrofluids exhibit excellent optical properties. The external magnetic source is installed to alter the thermo-physical properties of the fluid, and the absorber tube does not have selective surface allowing ferrofluids to absorb the incoming solar irradiance directly. In this paper, an experimental investigation of the performance of small scale direct absorption solar collector using ferrofluids as an absorber was conducted. Nanoparticle concentrations of 0.05 vol% at the operational temperatures between 19°C and 40°C were used in the current study. The results show that using ferrofluids as a heat transfer fluid increases the efficiency of solar collectors. In the presence of the external magnetic field, the solar collector efficiency increases to the maximum, 25% higher than the conventional parabolic trough. At higher temperatures, the ferrofluids show much better efficiency than conventional heat transfer fluid. The study indicated that nanofluids, even of low-content, have good absorption of solar radiation, and can improve the outlet temperatures and system efficiencies. The study shows the potential of using ferrofluids in the direct absorption solar collector. [ABSTRACT FROM AUTHOR]