Applications Of Ferrofluids Research Articles

Flexible Ferrofluids: Design and Applications.

Ferrofluids, also known as ferromagnetic particle suspensions, are materials with an excellent magnetic response, which have attracted increasing interest in both industrial production and scientific research areas. Because of their outstanding features, such as rapid magnetic reaction, flexible flowability, as well as tunable optical and thermal properties, ferrofluids have found applications in various fields, including material science, physics, chemistry, biology, medicine, and engineering. Here, a comprehensive, in-depth insight into the diverse applications of ferrofluids from material fabrication, droplet manipulation, and biomedicine to energy and machinery is provided. Design of ferrofluid-related devices, recent developments, as well as present challenges and future prospects are also outlined.

Theoretical analysis and experimental studies on torque friction in magnetic fluid seals

Magnetic fluid seals are among the most common applications of ferrofluids. In such seals, the torque friction results only from the internal friction in the fluid and there is no direct contact between seal elements. Despite this, the heat generated during operation can be significant due to the low volume of the ferrofluid in the seal and high rotational speeds. The difficulty in calculating the torque friction is because the ferrofluid is a non-Newtonian fluid and changes its viscosity under the influence of a magnetic field. In order to measure torque friction in magnetic fluid seals, a special test stand was built. Tests were performed at different rotation speeds, different temperatures, and two seal stage geometries (rectangle and trapezoid). Numerical simulations were performed to determine the magnetic field distribution in the seal. Dynamic viscosity under the influence of the magnetic field was measured on a rotary rheometer. Mathematical models were compared with laboratory results. The results obtained from the calculations in some cases gave overstated values almost twice in value. An additional correction in the case of ferrofluid viscosity is proposed.

Estimation of magnetic particle size distribution for ferrofluids based on nonlinear programming optimization and an improved Bayesian method

Abstract For the fundamental research and industrial application of ferrofluids, the particle size distribution (PSD) of magnetic nanoparticles is crucial to characterize their material properties. This work aims to develop efficient and robust PSD estimation methods for ferrofluids without interacting particles under two cases, known and unknown distribution types. The main task of the first case is to estimate the distribution parameters for a given PSD. For this purpose, Lp norm method is employed to convert the PSD estimation matrix equation into a constrained nonlinear programming problem. Then the nonlinear programming method (NPM) is presented to estimate the PSD parameters based on the magnetization data. The main tasks of the second case are to reconstruct the PSD curve and estimate the distribution type and parameters. To achieve these goals, an improved Bayesian method is proposed by using the estimation obtained from NPM as its prior information. Then a non-parameter hypothesis test method, Shapiro-Wilk test is introduced to determine the distribution type of the PSD. To illustrate the effectiveness of the proposed methods, theoretical analysis and Monte Carlo simulation are conducted based on the material parameters and experimental results of two ferrofluid samples. Through the comparison, it is found that the NPM is less sensitive to the noise like measurement errors and it can provide more accurate estimations than conventional inversion methods. Moreover, the proposed improved Bayesian method is efficient and robust to the noise, which can be used to reconstruct the PSD curves of ferrofluids without using the conventional time-consuming experimental methods like transmission electron microscopy.

예술 및 음악과 융합할 수 있는 재료로서의 나노 유체에 대한 연구

Nano science and nanotechnology has convergence with sports, music, and arts beyond convergence with other scientific technologies, and comes to develop into a totally new area. Ferrofluids feature the creation of the magnetic field induced shape on the ferrofluid surface, combination of drops, and magnetic microconvection. Because of its small particles size, a ferrofluid has been developed as a promising new nanomaterial the beginning. Ferrofluids are more applied to diverse areas, such as dynamic loudspeakers, computer hardware, dynamic sealing, and bioengineering because of their unique properties. The research method is as follows.BR Firstly, introduction of the background and scope of the study. The basic theories for ferrofluid science and examples of convergent work with ferrofluids are known and published.BR Secondly, the classification of magnetic fields are introduced. There are generally two type of magnetic fields which are magnetorheological fluids and ferrofluids. A ferrofluid is a colloidal suspension of magnetic particles with a very tiny size in a liquid carrier. A ferrofluid is different from MRF with regard to its fluidity even if subjected to strong magnetic fields.BR Thirdly, A key to the application of ferrofluids is colloidal stability. The stability is determined by the balance of multiple types of energy (attractive and repulsive forces) which are the factors to prevent separation for a given time after the disappearance of exterior magnetic fields and thermal energy. If average thermal energy exceeds a total of interaction, negligible agglutination arises. There are two types of ferrofluid which are water-based ionic fluid and organic media based ferrofluid. To use ferrofluid to convergent with arts or other areas, important factors are low viscosity, low vapor pressure and chemical inertness of carrier liquids and surfactants.BR Finally, There are many areas which convergent with ferrofluid to invent totally new work and to sell fantastical products which never meet before. Those areas are arts, music, sculpture, and commercial products. According to the development the nanotechnology, the convergence of ferrofluid with arts or other areas will be accelerate and develop further and intensively.

Magnetic detection of nanoparticle sedimentation in magnetized ferrofluids

Colloidal stability in external magnetic field is crucial for applications of ferrofluids. Here, we introduce a magnetic analysis approach to monitor how rapidly magnetic nanoparticles are pulled out of the liquid in an external magnetic field gradient. The motion of the sedimentation front is deduced from the time-dependent field produced by a column of ferrofluid placed on a permanent magnet. Citrate-stabilized nanoparticles in a homemade aqueous ferrofluid are found to sediment at the rate expected of single nanoparticles. More rapid sedimentation occurs in two other types of ferrofluid, indicating that our magnetic sedimentation analysis method can differentiate ferrofluids with respect to their in-field colloidal stability. Our method is further validated by comparison with time-dependent X-ray transmission profiles.

Experimental Study on the Pressure Distribution Mechanism Among Stages of the Magnetic Fluid Seal

One of the main engineering applications of ferrofluids is in magnetic fluid seals, working in rotary motion. An area, which has so far been insufficiently examined, is the mechanism of leaks between seal stages in this type of seal. This is an important issue in order to understand the principle of the seal operation and to properly design this type of seal. This paper presents the results of research into the mechanism of leaks between stages in multi-stage magnetic fluid seals. The tests were conducted when the pressure of the sealing air increased and reached its maximum value. The influence of the magnetic fluid properties, such as saturation magnetization or dynamic viscosity, was taken into account. Studies were performed for different seal temperatures. Experiments allowed models for determining the maximum pressure of the multi-stage seal to be proposed, based on the information about this pressure for a one-stage seal. This paper presents the comparative results of the critical pressure value obtained from experimental studies and calculations based on numerical simulations.

Synthesis of FeCoB amorphous nanoparticles and application in ferrofluids

Magnetic FeCoB amorphous nanoparticles were successfully synthesized by borohydride reduction in water/n-hexane (W/He) microemulsions. The as-prepared FeCoB alloys are amorphous and spherical nanoparticles with an average particle size about 10.7 nm, compared to FeCoB alloys with an average particle size about 304.2 nm which were synthesized by a conventional aqua-solution method. Furthermore, three kinds of FeCoB ferrofluids (FFs) were prepared by dispersing FeCoB particles into W/He microemulsion, water and silicone oil respectively. Results show that the W/He-based FeCoB FFs are superparamagnetic with saturation magnetization (Ms) reaching to 12.4 emu/g. Besides, compared to water-based and silicone oil-based FFs, W/He-based FeCoB FFs exhibit high stability, with magnetic weights decreasing slightly even under the magnetic field intensity of H = 210 mT. In the W/He-based FeCoB FFs, interfacial tensions of water phase and oil phase are supposed to prevent the agglomeration and sedimentation of FeCoB nanoparticles dispersed in different water droplets of the microemulsion, compared to the current stabilizing method of directly modifying the surface of particles.

Structure and room-temperature ferromagnetism evolution of Sn and Mn-doped NiO synthesized by a sol-gel process

Abstract The development of room temperature ferromagnetism is imperative for energy systems such as data storage in computers and spintronics. Herein we report a room temperature ferromagnetic study of Sn and Mn doped nickel oxide synthesized by sol gel method. The size and morphology of the samples are calculated using XRD and TEM analysis. The XRD and Fourier transform infrared (FTIR) results indicate that the synthesized NiO powders have a pure cubic structure. The variation in lattice parameters has been studied using the Rietveld refinement of X-ray diffraction pattern. The addition of dopants does not affect the structure of NiO. The presence of dopants in the doped NiO samples has been confirmed with Energy Dispersive Spectroscopy (EDS) analysis. The Photoluminescence (PL) spectrum shows enhanced luminescence intensity for Sn doped NiO than Mn doped NiO. The magnetic properties of the samples have been studied using Vibrating sample magnetometry (VSM). The pure and Mn doped NiO samples are found to exhibit ferromagnetism. The Sn doped NiO samples exhibit superparamagnetism making them suitable for applications in ferrofluids and as contrast agents for magnetic resonance imaging. The coercivity and magnetization of the Mn doped NiO samples are found to be enhanced compared to the pure NiO. The Sn doped NiO samples have very low value of coercivity compared with both pure and Mn doped NiO samples. The observed room temperature ferromagnetism in doped NiO makes it a suitable candidate for DMS devices such as MR imaging and magnetic delivery.

Damping Applications of Ferrofluids: A Review

Ferrofluids are a special category of smart nanomaterials which shows normal liquid behavior coupled with superparamagnetic properties. One of the earliest and most prospective applications of ferrofluids is in damping, which has prominent advantages compared with conventional damping devices: simplicity, flexibility and reliability. This paper presents the basic principles that play a major role in the design of ferrofluid damping devices. The characteristics of typical ferrofluid damping devices including dampers, vibration isolators, and dynamic vibration absorbers are compared and summarized, and then recent progress of vibration energy harvesters based on ferrofluid is briefly described. Additionally, we proposed a novel ferrofluid dynamic vibration absorber in this paper, and its damping efficiency was verified with experiments. In the end, the critical problems and research directions of the ferrofluid damping technology in the future are raised.

Effects of fluid inertia forces in ferrofluid lubricated circular stepped squeeze films – Shliomis model

Purpose This paper aims to study the inertia squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped squeeze films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated. Design/methodology/approach On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped squeeze films in the presence of external magnetic fields are investigated in this study. Analytical solutions of squeeze film performances are derived. Findings The fluid inertia force effects provide an increased load capacity and a longer squeeze film time for the ferrofluid-lubricated circular stepped squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio. Originality/value For engineering applications, numerical tables for squeeze film loads of circular stepped disks are also provided in this paper.

ChemInform Abstract: Recent Progress in Ferrofluids Research: Novel Applications of Magnetically Controllable and Tunable Fluids

AbstractReview: 221 refs.

Nanosized Fe3O4 an efficient PCR yield enhancer—Comparative study with Au, Ag nanoparticles

Nanomaterials-assisted PCR is a promising field of nanobiotechnology that amalgamates nanomaterials into the conventional PCR system to achieve better amplification of desired product. With literature documenting the variable effects of these nanomaterials on the PCR yield and amplification; it was thought worthwhile to compare the PCR enhancing efficiency of three transition metal nanoparticles in form of stable colloidal suspensions at varying concentrations.The nanoparticles(NPs) of silver, gold and magnetite were chemically synthesized by reducing their respective salts and characterized using UV–vis spectroscopy. Their morphology was assessed using nanoparticle tracking system and AFM. The effect of these nanofluids on amplification of 800bp prokaryotic DNA template with 30% GC content was studied using conventional thermal cycler. The reaction kinetics for all the three nanofluids yielded a Gaussian curve of amplification with varying concentrations. The ammonium salt of oleic acid coated magnetite (Fe3O4) nanoparticles at a concentration of 0.72×10−2nM and average size of 33nm demonstrated highest amplification efficiency of 190% as compared to the citrate stabilized AgNP-25nm (45%) and AuNP-15.19nm (134%) using a conventional PCR system. The major reasons that allow Fe3O4 NPs outperform the other 2 transition metal NP’s seem to be attributed to its heat conduction property as well as effective adsorption of PCR components onto the ammonium salt of oleic acid coated magnetite nanofluids. The data from our study offers valuable information for the application of ferrofluids as economically, efficient and effective alternative for nanomaterial-assisted PCR yield enhancers.

Band Structure Dependence on the External Perpendicular Magnetic Field and Zn Concentration of Photonic Crystals Made of Co1–xZnxFe2O4Nanoparticles

Ferrofluids based on the Co1– x Zn x Fe2O4 magnetic nanoparticles are considered as soft magnetic materials with interesting technological applications in nanotechnology when the ferrofluids are placed in an external magnetic field. The morphological characterization of Co1– x Zn x Fe2O4 magnetic nanoparticles was obtained by means of high-resolution transmission electron microscopy studies. In addition, we observed self-assembles of Co1– x Zn x Fe2O4 magnetic nanoparticle aggregates forming columns in a hexagonal 2-D photonic crystal (PC) when the ferrofluid was encapsulated in a cell glass under the action of a tunable magnetic field applied perpendicular to the film. The dependence of the ferrofluid effective refractive index with the applied magnetic field strength was determined by laser interferometry measurements using a Mach–Zehnder interferometer. To determine the optical response of 2-D magnetocontrollable PCs based on ferrofluids under the action of a dc external magnetic field, the Maxwell–Garnett theory, experimentally calculated effective refractive index, and plane-wave expansion method were used. The photonic band structure (PBS) of 2-D PCs for these ferrofluids was simulated, and we found that the optical response of PC depends on the ferrofluid effective refractive index, area ratio, permittivity of magnetic columns, and composition of Co1– x Zn x Fe2O4 ferrofluids. The results showed that the PBS of ferrofluid with the less Zn concentration ( $x = 0.25$ ) presented a complete bandgap in the IR range ( $\lambda \cong 10.6~\mu \text{m}$ ) at low perpendicular applied magnetic field. Finally, the procedure used in this paper may be considered as an alternative method to characterize the optical response of nanostructured ferrofluids in the presence of external magnetic fields. These results can be considered for technological applications of ferrofluids as magnetocontrollable PCs.

Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

Effect of hydrophilic silica nanoparticles on the magnetorheological properties of ferrofluids: a study using opto-magnetorheometer.

For many technological applications of ferrofluids, the magnetorheological properties require being precisely controlled. We study the effect of hydrophilic silica on the magnetorheology of an oil-based ferrofluid containing Fe3O4 nanoparticles of size ∼10 nm. We observe that the presence of silica nanoparticles lowers the yield stresses, viscoelastic moduli, and shear thinning behavior of the ferrofluid because of the weakening of dipolar interactions, which was evident from the observed lower yield stresses exponent (<2). The ferrofluid containing silica exhibits a dominant elastic behavior, a reduced hysteresis during the forward and reverse magnetic field sweeps, and a longer linear viscoelastic regime under nonlinear deformation. The Mason number plots at low shear rates and magnetic fields show deviations from the master curve in the presence of silica. The magnetic field induced microstructures, visualized using opto-magnetorheometer, showed columnar aggregate structures along the field directions, which are reoriented along the shear flow direction at high shear rates. The image analysis shows that the average thickness of the columnar aggregates in pure ferrofluid is much larger than that of the mixed system, which suggests that the intervening silica matrix hampers the zippering transition of columns at higher magnetic field and shear rates. Our results suggest that optimization of rheological properties of ferrofluids is possible by carefully adding suitable silica nanoparticles, which may find practical applications such as dynamic seals, heat transfer, sensors, and opto-fluidic devices, etc.

Recent progress in ferrofluids research: novel applications of magnetically controllable and tunable fluids.

Ferrofluids are suspensions of magnetic nanoparticles that have the attractive feature of being controlled by applied magnetic fields. Ferrofluids have been studied for decades in an ever growing number of applications that take advantage of their response to applied magnetic fields. Here, we provide a summary of recent advances in established and emerging applications of ferrofluids, including applications in optics, sensors, actuators, seals, lubrication, and static/dynamic magnetically driven assembly of structures.

A facile synthesis of flower-like α-Fe2O3/Cu nanocomposites and their magnetic properties

Novel flower-like α-Fe2O3/Cu nanocomposites were prepared by a facile, direct subsidence loading method. The composition and morphology of the obtained samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The morphology and structure of such novel products strongly depended on the reaction temperature and the amount of iron oxide. The size of copper nanoparticles which loaded on the α-Fe2O3 flower petals was ca. 100nm. Room temperature magnetic measurement of the flower-like nanocomposites demonstrated its ferromagnetic properties and the saturation magnetization (Ms) decreased from 0.33 to 0.09emu/g. The results showed a potential application in ferrofluids and other related electromagnetism devices.

Fabrication of hollow spheres FeCo alloy through a hydrothermal reduction method

Hollow spheres like FeCo alloy were synthesized by a hydrothermal method without using any templates or external magnetic field. The morphology and size of final products strongly depend on the reaction temperature and hydrazine hydrate concentrations. The structures and shapes of as-prepared samples were investigated by XRD, SEM, and EDS techniques in detail. The formation of such novel FeCo alloy was discussed on the basis of controlled experiments. The magnetic measurement demonstrated that the hollow spheres FeCo alloy exhibited ferromagnetic nature with saturation magnetization of 169.35emu/g and coercivity of 528.5Oe, respectively. Moreover, the FeCo alloy shows high wave-absorbing properties (e.g., −18.3dB), which are expected to be applied in microwave absorbing materials. Those results showed a potential application in ferrofluids and other related magnetic devices.

Preparation and magnetic properties of single phase Ni2Si by reverse Rochow reaction

Single phase Ni2Si nanoparticles (NPs) have been successfully synthesized by using the Rochow reverse reaction, in which organosilanes ((CH3)nSiCl4−n) are used as the silicon source. The results demonstrate that the crystalline size and phase of nickel silicide can be controlled through changing the organosilanes and reaction time. A formation mechanism of Ni2Si NPs has been proposed, which involved reaction deposition and subsequently diffusion of Si atoms. Magnetism performance tests indicate that the saturation magnetization and coercive field of Ni2Si NPs depend greatly on the environmental temperature and particle size. The blocking temperature (TB) of the materials was found to strongly depend on selecting the organosilanes precursor: in the case of the Ni2Si-0 (148 K) and Ni2Si-2 (336 K). This novel methodology opens a route to prepare other classes of metal silicides with single phase and stoichiometry. The as-prepared single phase Ni2Si nanoparticles can find applications in ferrofluids, imaging, and magnetic separation due to its special magnetic behavior depending on the applied temperature (below or above TB).

PHOTOLUMINESCENCE SPECTRA AND MAGNETIC PROPERTIES OF HYDROTHERMALLY SYNTHESIZED MnO2 NANORODS

In this paper, single crystalline tetragonal MnO 2 nanorods have been synthesized by a simple hydrothermal method using MnSO 4⋅ H 2 O and Na 2 S 2 O 8 as precursors. The crystalline phase, morphology, particle sizes and component of the as-prepared nanomaterial were characterized by employing X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDS). The photoluminescence (PL) emission spectrum of MnO 2 nanorods at room temperature exhibited a strong ultraviolet (UV) emission band at 380 nm, a prominent blue emission peak at 453 nm as well as a weak defect related green emission at 553 nm. Magnetization (M) as a function of applied magnetic field (H) curve showed that MnO 2 nanowires exhibited a superparamagnetic behavior at room temperature which shows the promise of synthesized MnO 2 nanorods for applications in ferrofluids and the contrast agents for magnetic resonance imaging. The magnetization versus temperature curve of the as-obtained MnO 2 nanorods shows that the Néel transition temperature is 94 K.