Water-based Magnetic Fluid Research Articles

Magneto-optically induced retardation and relaxation study in a mixed system of magnetic fluid and cationic micelles

Stable colloidal systems composed of a double surfactant water-based magnetic fluid mixed with a cationic isotropic micellar solution of cetyletrymethyleammonium bromide (CTABr) are prepared for different concentrations of magnetic fluid. The structural integrity between nanomagnetic particles of magnetic fluids and soft micelles is investigated using the magneto-optical techniques like magnetic birefringence, transmission and relaxation measurements. Magneto-optically induced retardation and relaxation measurement indicates the existence of magnetically induced interactions in this mixed system. Similar behaviour is also observed in small angle neutron scattering experiments.

Ultrasonic determination of the particle size distribution in water-based magnetic liquid

Magnetic liquids are stable colloidal suspensions of nano-sized magnetic particles in a carrier liquid medium. In the present paper the determination of the particle size distribution function using ultrasonic spectroscopy is described. The ultrasonic spectra of water-based magnetic fluid measured in the 3.5–50 MHz frequency range are analyzed using formulas for the velocity and absorption of sound in dispersion media obtained by Vinogradov. The results of the ultrasonic studies are compared with the particles size distribution function evaluated from the processing of the magnetic susceptibility data

Surfactant double layer stabilized magnetic nanofluids for biomedical application

Magnetite nanoparticles were coated with surfactant double layers in order to prepare waterbased magnetic fluids (MFs). The effects of head group (sulfonate, carboxylate) and alkylchain length (11–17 C atoms) and the combination of surfactants were studied. Adsorption,dynamic light scattering (DLS) and electrophoretic mobility measurements were performed.The quantity of surfactant varied between 0.3 and 0.5 g, i.e. their specific amount ranges over1.5–2 mmol g−1 magnetite in MFs. The adsorption isotherm of Na oleate on magnetite proved the double layer formationwith 2 mmol g−1 saturation value in good harmony with the empirical doses. The effect of diluting MFs, pHand salt concentration was studied. The pH-dependent stability and the salt tolerance ofMFs were different owing to the dissociation of the outermost hydrophilic groups and thehydrophobic interactions scaling with the alkyl chain length of surfactant. Thehydrophobic interactions are favored only for oleic and myristic acid double layers. Inthese MFs, aggregation cannot be observed even in fairly dilute systems up to thephysiological salt concentration around neutral pH 6–8 favored in biomedicalapplication. The stable oleic and myristic acid double layers can hinder effectively theaggregation of magnetite particles due to the combined steric and electrostaticstabilization.

Preparation and properties of water-based magnetic fluids

Stable suspensions of superparamagnetic iron oxide nanoparticles in water (water-basedferrofluids) were prepared using citric acid (CA) as a surfactant. The influences of differentfactors on the amount of nanoparticles in a stable suspension were systematically studied.These factors, including the temperature, the pH value and the concentration of CAapplied during the adsorption of the CA onto the nanoparticles and during their suspensionin water, were evaluated. The highest content of nanoparticles in a stable suspensionwas obtained when the CA was absorbed at pH values of around 5.2, where twocarboxyl groups are dissociated, and when the nanoparticles were suspended at a pHof around 10, where all three carboxyl groups of the CA are in a dissociatedstate.

Controllable modification of the lignocellulose fiber surface with a water-based magnetic fluid

Controllable modification of the lignocellulose fiber surface with a water-based magnetic fluid

A novel method for the preparation of stable bilayer-coated magnetite particles for hyperthermia

Stable water-based magnetic fluids were synthesized by a sequential process involving the co-precipitation of Fe 3 * and Fe 2 + with NH 3 H 2 O to prepare magnetic particles, then two stabilizers, sodium oleate (SO) and Dextran T-40, were used to coat the particles. The prepared magnetic particles were stabilized against agglomeration by the bilayer structure formed by SO, as an inner layer, adsorbed firmly onto the surface of the magnetic particles by hydrogen bonding, and dextran T-40, as an outer layer, interacted with SO in the same way, which were confirmed by Fourier transform infrared (FT-IR). The particle morphology and size were characterized using transmission electron microscopy (TEM), indicating the formation of single-domain nanoparticles with a mean diameter of about 26.1 nm. The saturation magnetization (Ms) value of 42.1 emu/g was obtained by vibrating sample magnetometry (VSM). Also, X-ray powder diffraction (XRD) analysis showed that the powder phase was almost entirely magnetite. The bilayer-coated magnetic fluid can be used as a therapeutic agent to release thermal energy as determined in hyperthermic tests.

PROPERTIES OF ULTRASONIC PROPAGATION IN FUNCTIONAL FLUIDS UNDER MAGNETIC FIELDS

The properties of ultrasonic propagation velocity in water-based and kerosene-based magnetic fluids and an MR fluid are examined experimentally. The ultrasonic frequency used is 1 MHz and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0 mT to 550 mT and is swept at a constant rate dB/dt (sweep rate). The ultrasonic propagation velocity changes with applied magnetic field and hysteresis is observed. The properties of ultrasonic propagation seem to be highly influenced by the formation of chain-like clusters (in the magnetic fluids) and robust clusters (in the MR fluid).

Magnetic studies of ferrofluid-modified spruce sawdust

Spruce sawdust (lignocellulose material) was magnetically modified after contact with a water-based magnetic fluid containing maghemite nanoparticles. This procedure allows one to use the prepared material as a new magnetic affinity adsorbent in magnetic separation techniques. The magnetic sawdust was investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4–300 K.The experimental results clearly show that the magnetic behaviour of the sample is determined by two distinct magnetic contributions. One of them is connected to the presence of isolated single domain maghemite nanoparticles of ∼11 nm in diameter, which exhibit superparamagnetic behaviour at T > 280 K. The other one is related to the presence of agglomerates of particles coupled by magnetic dipolar interactions.

Investigation of the non-linear loss properties of magnetic fluids subject to large alternating fields

The non-linear relaxational properties of a water-based magnetic fluid are investigated by means of measuring the frequency dependent complex susceptibility, χ( ω) in the presence of an external potential. The results obtained are discussed in terms of the magnetic analogue of the Coffey and Paranjape model as modified by Déjardin. The loss processes in the magnetic fluid in the non-linear region are investigated in the context of the loss tangent, tan( δ), and the power dissipation per unit volume. These measurements are of importance because of the continuing interest in the clinical applications of magnetic fluids, where large alternating magnetic fields can be applied to magnetic fluids to induce loss processes and heating effects, often driving the magnetic fluid into the non-linear region of magnetisation. We evaluate the increment of the susceptibility, Δ χ, due to the non-linear response, through measurement of χ( ω), and extend this formulism to the non-linear increment of the loss tangent, Δ tan( δ) and the increment of the heating rate, Δ U heat.

Acute toxicity and irritation of water‐based dextran‐coated magnetic fluid injected in mice

Based on the elements that magnetic nanoparticles could heat in an alternating magnetic field, magnetic fluid hyperthermia occurred to inhibit tumor growth in vivo. However, biocompatibility of those fluids as well as the fluid-body interaction remains unclear. In this article, acute toxicity and irritation of the water-based dextran-coated magnetic fluid (dextran-magnetic fluid) injected into mice subcutaneous tissues were examined. Lethal dosage 50 of single treatment with the magnetic fluid was 4409.61 +/- 514.93 mg/kg. When injected with 30 mg/0.3 mL dextran-magnetic fluid, activities of glutamicoxalacetictransaminase (AST) and glutamicpyruvictransaminase (ALT) and cell number of mice blood did not change statistically. Hemangiectasia and leucocytes infiltration were seen in subcutaneous tissues and these phenomena almost disappeared 72 h later. That is to say, the dextran-magnetic fluid was tolerable, safe, and biocompatible. The work is a basic for application of the dextran-magnetic fluid in subcutaneous tumor therapy.

Influence of a uniform magnetic field on ultrasonic propagation velocities in magnetic fluids

Experimental results for ultrasonic propagation velocity properties in water-based magnetic fluids are reported. Water-based magnetic fluid samples having 10 wt%, 20 wt%, 30 wt% and 40 wt% concentration of magnetic particles were examined. The ultrasonic propagation velocity generally decreases with higher concentrations of magnetic particles, generally increases with increasing external magnetic field intensity and exhibits anisotropy.

Adsorption of water-soluble organic dyes on ferrofluid-modified sawdust

Abstract A magnetically responsive composite material based on lignocellulose and magnetic nanoparticles has been prepared. Spruce sawdust was magnetically modified by contact with water-based magnetic fluid stabilised with perchloric acid. Electron spin resonance and transmission electron microscopy measurements indicated the presence of both individual magnetic nanoparticles and clusters precipitated on the surface of sawdust particles. The material prepared was used to study the adsorption of selected water-soluble organic dyes. The adsorption isotherms followed Langmuir, generalised Freundlich, generalised Langmuir, and Langmuir-Freundlich adsorption patterns. Maximum adsorption capacities for acridine orange, Bismarck brown, crystal violet, malachite green, methyl green, Nile blue, safranin O and Saturn blue LBRR 200 ranged between 34 and 59 mg g-1 dry adsorbent. A change in pH value can increase the dye adsorption. Ferrofluid-modified sawdust is thus an interesting material for further study and potential applications.

Experimental and numerical investigations on magnetic fluid jet

The rheological properties of water-based magnetic fluids (MFs) were measured using rotating and capillary rheometers. It is found that the theological behaviors of MFs with high solid content under an applied magnetic field can be described using the Herschel-Bulkley (H-B) model. Two-dimensional numerical simulation was performed to investigate ejection phenomena of the MF from a capillary with the H-B model. Experiments was conducted to observe drop formations. The measured numerical results are validated by the experimental findings.

Magnetic-field-induced birefringence and particle agglomeration in magnetic fluids

Birefringent effect dependent on magnetic intensity and wavelength in a water-based Fe3O4 magnetic fluid over the wavelength range of 400–700nm is studied in this letter. The results are compared with the theory proposed by Llewellyn [J. Phys. D 16, 95 (1983)], in which the optical anistropic properties of the magnetic fluid due to the aggregation of the particles at a relatively low density is suggested. It is shown that the degree of aggregation corresponds to the value of the axial ratio of the aggregated particles. So does the magnitude of the birefringence.

New magnetically responsive yeast-based biosorbent for the efficient removal of water-soluble dyes

Fodder yeast ( Kluyveromyces fragilis) cells were magnetically modified by a contact with the water-based magnetic fluid in order to prepare a new type of magnetically responsive biocomposite material. This procedure enabled a simple separation of modified cells by means of commercially available magnetic separators or strong permanent magnets. It allows using the prepared material as a new inexpensive magnetic affinity adsorbent for the removal of water-soluble dyes. Magnetically modified cells were characterized by means of magnetic and microscopy methods. Both isolated magnetic nanoparticles and aggregates of particles were present on the cell surface. The prepared material displayed a superparamagnetic behavior at room temperature, with a transition to a blocked state at T B ∼ 180 K for the applied magnetic field H = 50 Oe. Seven dyes (crystal violet, amido black 10B, congo red, Saturn blue LBRR, Bismarck brown, acridine orange and safranin O) were used to study the adsorption process. The dyes adsorption could be described with the Langmuir isotherm. The maximum adsorption capacities ranged between 29.9 (amido black 10B) and 138.2 (safranin O) mg of dye per g of dried magnetically modified cells.

Ferromagnetic resonance investigation of maghemite-silica nanocomposites

Maghemite-silica nanocomposites were prepared from water-based magnetic fluids through the sol-gel method. X-ray diffraction revealed that the maghemite nanoparticles had a size of 5nm. Electron magnetic resonance of the composites was studied as a function of temperature and nanoparticle concentration. The resonance field was found to decrease upon increasing the maghemite concentration, while the linewidth increased. The effect was interpreted in terms of interparticle as well as intraparticle magnetic interactions. The data analysis suggests the presence of small agglomerates in the maghemite-silica nanocomposite for higher particle concentrations.

Citric-acid-coated magnetite nanoparticles for biological applications

Water-based magnetic fluids, generally intended for biomedical applications, often have various coating molecules that make them stable and compatible with biological liquids. Magnetic fluids containing iron oxide particles have been prepared by a co-precipitation method, using citric acid as stabilizer. The magnetic particles of the magnetic fluids were obtained by chemical precipitation from ferric (FeCl(3)) and ferrous salts (FeSO(4) or FeCl(2)) in alkali medium (ammonia hydroxide). Citric acid was used to stabilize the magnetic-particle suspension. Physical tests were performed in order to determine various microstructural and rheological features. Transmission electron microscopy was the main investigation method for assessing the magnetic-particle size. The dimensional distribution of the magnetic-particle physical diameter was analyzed using the box-plot statistical method while infrared absorption spectra were used to study the colloidal particle structure. The magnetic-fluid density (picnometric method), viscosity (capillary method) and surface tension (stalagmometric method) were measured using standard methods.

Deformation and motion by gravity and magnetic field of a droplet of water-based magnetic fluid on a hydrophobic surface

Motion and deformation of a water-based magnetic fluid on a hydrophobic surface were investigated under gravity and a magnetic field. Surface energy and the resultant contact angle of the magnetic fluid depend on the surfactant concentration. The fluid viscosity is governed mainly by magnetite concentration. The front edge of the droplet moved under a weak external field. The rear edge required a higher external field for movement. The forces of gravity and the magnetic field for moving of the front edge are almost equal. However, those of the rear edge are different. The motion of magnetic fluids by an external field depends on concentrations of surfactants and magnetic particles, the external field, and experimental assembly.

Cluster formation of ferromagnetic nano-particles in micro-capillary flow

This paper reports the experimental research on the growth and dispersion processes of cluster formation in a water-based magnetic fluid in micro-capillary flow. The magnetic fluids are suspensions of ultra fine particles coated with a molecular layer of dispersant in a liquid carrier, such as water or kerosene. The ultra fine particles are coated with single- or double-layer surfactants to attain stable dispersion. However, numerous experimental studies have indicated the existence of primary cluster of ferromagnetic nano-particles in a water-based magnetic fluid. The purpose of this research is to observe the characteristics of primary clusters in micro-capillary flow. The thermal behavior of ferromagnetic nano-particles in micro-capillary flow was observed through micro-visualization using the optical dark-field microscope system and particle tracking velocimetry (PTV) data processing system. Real-time visualization of the Brownian motion of primary clusters in a water-based magnetic fluid in micro-capillary flow was carried out. Furthermore, the effect of magnetic field on the growth process and dispersion process of cluster formation in micro-capillary flow was investigated.

Micro Capillary Flow of Magnetic Fluid and Flow Control using Magnetic Field

This paper reports the experimental research on micro-visualization of the growth process of cluster formation of ferromagnetic nano-particles in a water-based magnetic fluid on micro capillary flow. The purpose of this research is to observe the characteristics of primary clusters in micro capillary flow. The thermal behaviour of ferromagnetic nano-particles in micro capillary flow was observed through micro-visualization using the optical dark-field microscope system and particle tracking velocimetry (PTV) data processing system. Real-time visualization of primary clusters in a water-based magnetic fluid on micro capillary flow was carried out. Furthermore, the effect of magnetic field on the mixing process of using a water-based magnetic fluid in micro capillary flow was investigated.