Magnetite Magnetic Fluid Research Articles

Tunable birefringence in silica mediated magnetic fluid

The present study reports magnetic and optical properties of silica mediated lauric acid stabilized magnetic fluids. The tunable birefringence (Δn) and other properties are investigated as a function of (i) concentrations of silica suspension, and (ii) saturation magnetization (MS) 0.5099 kA m−1 (FN30) and 1.2855 kA m−1 (F30) of magnetite magnetic fluid (MF). The study reveals that Δn suppresses on addition of silica in FN30, whereas enhances (up to critical concentrations of silica) in F30. The magnetic field induced chain observed in the FN30 based fluids are long, thick and scattered, while short, thin and dense chains emerges in F30 based fluid. The magnetic field induced assembly and the magnetic parameters correlates with the results of Δn. The particle size analysis indicates increment of particle size on addition of silica nanoparticles. The thermogravimetry analysis confirms the direct interaction of silica nanoparticles and the lauric acid coated magnetite particles. This is the first report of direct interaction of silica—magnetite magnetic fluids, and its subsequent effect on tunable birefringence and other properties.

A universal magnetic ferrofluid: Nanomagnetite stable hydrosol with no added dispersants and at neutral pH

A facile method to produce highly stable magnetite magnetic fluid at neutral pH without any stabilizing agents, resulting in pure Fe3O4 nanoparticles dispersed in water is described. The hydrosol which consists of only two components – magnetite and water – behaves as a typical ferrofluid, that is, although it responds to a magnetic field, the magnetic particles cannot be phase-separated from the water by that field. No such pure magnetic fluid have been described before, making it a universal carrier which can be easliy modified for any application in materials science and chemistry, and in particular for a range of applications where non-corrosivity, low viscosity, and mild conditions are needed, such as in most bioapplications and in nano electro-mechanical systems. Under optimal conditions the hydrosol is stable for at least three months.

Field-induced flocculation on biocompatible magnetic colloids

Field dependence of the optical transmission of a polyaspartic-coated magnetite magnetic fluid dispersed in water was investigated at different particle volume fractions. The particle size distribution of the sample was obtained from the analysis of the transmission electron microscopy pictures. The transmissivity decreased increasing the magnetic field until a critical field is achieved. Above this value, the opposite effect was observed. Indeed, the critical field decreases the higher the particle volume fraction being in qualitative similarity with phase separation behavior. However, the origin of the effect is attributed to the precipitation of field-induced nanoparticle chains. These phenomena might be useful on obtaining one-dimensional nanoparticle arrangements.

Magnetic nanocomposites for sorbents and glue layers

Magnetic properties were added to original materials via impregnation with magnetic fluids, layer-by-layer (LbL) assembly of magnetite nanoparticles with polyelectrolytes or admixing to adhesive solutions. Thin multilayers with controllable thickness were formed on glass surfaces and lignocellulose fibers by the LbL method. Magnetic sorbents were created by impregnation of activated charcoal with a magnetite magnetic fluid stabilized with triethanolamine oleate. A mechanism of sorbent interaction with the nanoparticles is proposed. Possible application of these aqueous magnetic fluids for the formation of glutinous magnetic layers on metallized foil is demonstrated.

Complex magnetic susceptibility measurement of a magnetic fluid magnetite based

In this work, we present the synthesis and measurement of complex magnetic susceptibility χ(ω) = χ'(ω) - χ"(ω) of a magnetite magnetic fluid, oleic acid-kerosene. Measurements were developed applying different magnetic polarising fields by means of an electromagnet. Short-circuited transmission line technique was used. Complex magnetic susceptibility measurements of magnetic fluids are presented as a function of both frequency and external polarising magnetic field in ranges from 60 MHz to 6 GHz and from 0 Oe to 1212 Oe, respectively. Resonance frequencies in the range from 2.09 GHz to 5.06 GHz and maximum frequencies in the range from 1.19 GHz to 4.68 GHz as a function of the bias polarising field were measured for the magnetic fluid. From resonance measurements for different polarising fields, a mean anisotropy field value of A= 767Oe was obtained. Also a mean value of anisotropy constant = 12.2x104erg/cm3 and gyromagnetic ratio γ = 16.07 x 106 1/sOe were determined.

Field-induced diffraction patterns in a magneto-rheological suspension

Fraunhoffer diffraction patterns induced by external magnetic field in a magneto-rheological suspension of micron-sized magnetite particles in a stable kerosene-based magnetite magnetic fluid are studied. It is observed that the patterns significantly change with increase in the field and at a critical field the patterns completely disappears. With further increase in the field it again reappears. Magnetically induced extinction is also observed for this suspension. The extinction exhibits reversal with increase in the field when electric vector of incident light is perpendicular to the direction of the field. A possible explanation of this effect is discussed.

Characterization of inherent clusters in water-based magnetite magnetic fluid

In this paper, we report the results on particle structure in water-based magnetic fluid (MF) using scanning probe microscope (SPM), dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The SPM analysis showed the presence of ring structures. Furthermore, the DLS measurements indicated the presence of particles as large as few hundred nanometers. The SAXS measurements suggested that the clusters are formed in water-based MF although the primary unit is similar to oil-based MF. The size and proportion of the clusters depended on the dispersion mechanism.

An experimental and numerical investigation of flat panel display cell using magnetic fluid

Optical and fluid dynamical properties of magnetic fluid have been studied experimentally and numerically using a test device with a water-base magnetite magnetic fluid. It has been found that the 3.5 μm thick fluid film absorbs most of the incoming visible light and can be actuated fast enough to realize display devices. The computational simulation shows that the surface tension of the liquid plays the most dominant roles for the test device, and a device that can actuate the magnetic fluid magnetically is proposed.

Structure of particle assembly in water-based magnetite magnetic fluid under zero applied field

The magnetic particle dispersion in magnetic fluid has been found to depend very much on the type of dispersing media. The water-based magnetic fluid has been found to contain large number of inherent clusters even in zero applied magnetic field. In this paper, we discuss the possible origin of these primary clusters and propose that these clusters are of magnetic origin. The scanning probe microscope observation of primary clusters were carried out and found to be of ring shape.

An experimental study of light modulator using magnetic fluid

A type of light modulator using light-absorbing magnetic fluid has been studied experimentally. The basic operation principle and design of the modulator are addressed. It is shown that the luminance of the device can be modulated by applying a moderate level of electric current to a light-reflecting metal electrode. A high contrast ratio comparable to that of printed material was obtained using a kerosene-base magnetite magnetic fluid with a saturation magnetization of 196 G and a thickness of around 20 μm. Doubling of the luminance from a minimum level takes about 200 ms for a driving current of 80 mA. The operation speed of the cell was found to increase almost exponentially with driving current, suggesting the possibility of motion picture applications.

Rheological properties of magnetite magnetic fluid

The magnetic and rheological properties of magnetite magnetic fluids of different concentrations and dispersions have been investigated. The dispersion of the samples was varied in magnetite precipitation stage as well as by using HGMS. Like the concentration, the fluid dispersion also affects the rheological properties in an applied field.

Magneto-optics of ferrofluids, using fiber optics

A technique has been developed whereby only a small amount of a magnetic fluid is needed for optical measurements of magnetically induced birefringence and other magneto-optic effects. The ac field dependence of magnetically induced birefringence in a water based magnetite magnetic fluid is reported.