Surface Of Magnetite Particles Research Articles

Preparation of silver nanoparticles on the surface of fine magnetite particles by a chemical reduction

We demonstrate a modified polyol process to synthesize silver nanoparticles on the surface of larger magnetite nanoparticles. The overall process consists of two step reactions. First the magnetite particles of 100–200 nm in diameter are functionalized with a coupling agent 3-mercaptopropyltrimethoxysilane (MPTMS) through a sol–gel reaction. The functionalization of the magnetite surface is confirmed with IR spectra. For the second step silver nitrate is reduced at the site of thiol groups of the functionalized magnetite surface with ethylene glycol (EG) and polyvinylpyrrolidone (PVP). It was observed that silver nanoparticles were formed on the surface of the magnetite particles from transmission electron microscopy images and chemical composition analysis with energy dispersive spectrometer.

Synthesis and characterization of magnetite particles covered with α-trietoxysilil-polydimethylsiloxane

New silicon magnetite ferrofluids were prepared by dispersing siloxane-coated magnetite particles in polydimethylsiloxane with low or high molecular weights. Ferrofluids are stable colloidal dispersions of ultra fine covered magnetite particles, which may be selected for a specific application. We demonstrated new methods of stabilizing the magnetic particles by reacting the hydroxyl groups on the surface of magnetite particles with terminal ethoxy groups of polydimethylsiloxane, followed by their dispersion in silicon fluids. The new silicon ferrofluids were tested from the morphology, magnetic properties/losses, and rheological properties point of view.

Glycidoxypropylsilane-functionalized Magnetite as Precursor for Polymer-covered Core-shell Magnetic Particles

Surface-functionalized core-shell magnetic particles were obtained by reacting the hydroxyl groups on the surface of pre-prepared magnetite particles with 3-glycidoxypropyltrimethoxysilane. Fourier transform infrared spectra indicated that epoxy silane molecules were chemically bound onto the surface of magnetite particles through Fe—O—Si linkages. As proved by atomic force microscopy and environmental scanning microscopy combined with energy dispersive X-ray spectroscopy, particles with average core diameter and shell width of about 700 and 70 nm, respectively, were obtained. The covered magnetite particles showed a lower saturation magnetization (46 emu g 1) as compared to the uncoated magnetite (64 emu g 1).

Fabrication and Dispersion of Gold-Shell-Protected Magnetite Nanoparticles: Systematic Control Using Polyethyleneimine

A detailed study of the aqueous synthesis of composite 50−150 nm magnetite−gold core−shell nanoparticles with the ability to engineer the coverage of gold on the magnetite particle surface is presented. This method utilizes polyethyleneimine for the dual functions of attaching 2 nm gold nanoparticle seeds onto magnetite particles as well as preventing the formation of large aggregates. Saturation of the magnetite surface with gold seeds facilitates the subsequent overlaying of gold to form magnetically responsive core−shell particles, which exhibit surface plasmon resonance. In-depth characterization and quantification of the gold-shell formation process was performed using transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and inductively coupled plasma optical emission spectroscopy. Dynamic light scattering studies also showed that PEI coating of synthesized particles served as an excellent barrier against aggregation. The ability of the gold shell to pro...

Dispersion mechanism of nano-magnetite coated with oleate in aqueous carrier

To investigate dispersion mechanism of water-based ferrofluid, the effects of electrolytes on the dispersibility of ferrofluid in the dispersing system with different pH values were discussed. The ζ-potential of magnetic nano-particles was measured to discover the adsorbent state of oleate group on the surface of magnetite particles. The mechanism that coexisting electrolyte influences the dispersibility was studied. The results show that the electrolyte affects the stability of ferrofluid through an effect on the structure of surfactant bilayer adsorption, which was proved by ζ-potential measured. The associated mechanism of steric and electrostatic is dominant in aqueous ferrofluid.

The study on magnetite particles coated with bilayer surfactants

Magnetite particles were prepared by co-precipitation, then sodium oleic (SO) and sodium dodecyl benzene sulfonate (SDBS) were applied as inner and outer surfactants, respectively. IR and TG were used to study the surface adsorption of SO and SDBS on magnetite particles. The experimental results demonstrated that SO molecules were linked to the magnetite particles through chemical bond and SDBS coated on the surface of magnetite particles covered with SO by means of Van der Waals attraction. Furthermore, based on the adsorption isotherms of surfactants on the magnetite particles and the dependence of Zeta potential of particles on the surfactants concentrations, the adsorption mechanisms of these two surfactants on the magnetite particles were studied. The isotherm adsorption model for SO on magnetite particles showed excellent correlation to Langmuir type and the adsorption equation was Γ = 0.162 c 1 + 0.303 c (25 °C), while that for SDBS on magnetite particles coated with SO showed excellent consistence with Freundlich type and the adsorption equation was Γ = 0.32 c 0.475 (25 °C). In addition, the results demonstrated that both SO and SDBS formed monolayer adsorption on the surface of magnetite particles.

ドラッグデリパリーを目指したハイドロタルサイトの高機能化

Intercalation on hydrotalcite has been expected to apply for the drug delivery system. Osteoblast was cultivated in the culture solution dispersed hydrotalcite-ATP intercalation compound. The cells expanded in volume after 3 h cultivation. Hydrotalcite was not toxic and a part of it can be incorporated in the osteoblast. Fine size of hydrotalcite crystals is necessary for its endocytosis. Their fine crystals of < 50 nm were obtained in the precipitation from aqueous solution in strong magnetic field of 5 T applied vertically to the gravity. The intercalated drug should be concentrated at the diseased part. Magnetic hydrotalcite can be transferred by an external magnetic field to the part. Hydrotalcite was firmly bonded on the surface of magnetite particles by firing its coated complex at 400°C in nitrogen atmosphere.

Composite of polyaniline containing iron oxides

A composite of polyaniline (PANI) containing iron oxides with nanometer size was prepared by a chemical method. Polymer adsorption on the surface of magnetite particles was investigated. The electrical and ferromagnetic properties of the composites were measured as a function of the pH value of the reaction solution during polymerization. The conductivity of the composites at room temperature decreases with the increase of the pH as the doping level in the composite decreases. For the basic preparation conditions, the resulting PANI-Fe x O y composite can be attracted by a magnet at room temperature and shows an insulating behavior. Doping of PANI with acids leads to electrical conducting properties of ferromagnetic composites.

Effect of water chemistry, water treatment and Blaine on magnetite filtering and magnetite agglomeration with bentonite clay

This paper represents a synopsis of five referenced research projects conducted by the author. Included are summaries of problems that occur during agglomeration and filtering due to water chemistry, water treatment and magnetite-particle surface area. High concentrations of divalent-cations in process water, particularly calcium and magnesium, have severe detrimental effects on prefired pellet quality when bentonite clay is the pellet-binding agent. The presence of fluoride, sulfate and calcium in process water can negatively affect filtering. Chemical water treatment can affect agglomeration and filtering either negatively or positively, depending on the ions that are being removed from or added to the process water. Water-treatment mechanisms that ensure improved filtering and improved prefired pellet quality are described.

Development of a Colloid Chemical Process for Magnetic Seeding to Organic Dye

Abstract The recovery of organic dye molecules was achieved by using a colloidal magnetic seeding process under high-gradient magnetic separation. The recovery fraction of dye molecules was dependent on the adsorption capacity of the dye molecules. A magnetic colloid can recover a much greater amount of dye molecules than magnetite particles. The adsorption of orange II molecules was found to be an irreversible process, and orange II molecule could be more tightly adsorbed on a magnetic colloid than a magnetite particle surface.

Preparation and characterization of magnetite nanoparticles coated by amino silane

Magnetite nanoparticles were prepared by coprecipitation of Fe 2� and Fe 3� with NH4OH, and then, amino silane was coated onto the surface of the magnetite nanoparticles. Transmission electronic microscopy shows the average size of 7.5 nm in diameter. Powder X-ray diffraction and electronic diffraction measurements show the spinel structure for the magnetite nanoparticles. FT � /IR spectra indicate that amino silane molecules have been bound onto the surface of the magnetite nanoparticles by Fe/O/Si chemical bonds. Energy dispersive X-ray spectroscopy (SEM � /EDS) indicates atomic ratio of 96.75:3.25 for Fe:Si, implying a nearly monolayer coating of amino silane on the magnetite particle surface according to a rough calculation. By an enzyme-linked assay, it was proved that the amino silane-coated magnetite nanoparticles could significantly improve the protein immobilization. # 2002 Elsevier Science B.V. All rights reserved.

A Study on The Fabrication of Ultra Fine Magnetite Particles and Magnetic Fluid from the Waste Pickling Liquor of Steel

Ultra fine magnetite particles, with the mean particle size of 75A, were produced at pH 12 after adjusting the mole ratio of Fe2+/Fe3+ to 0.5 by partial oxidation of the waste pickling liquor of steel. After double adsorption of oleic acid ion and dodecyl benzene sulfonate (D. B. S) ion on the surface of magnetite particles, magnetite hydrophilic magnetic fluid was produced by dispersing the magnetite particles in ethylene glycol solution. The ethylene glycol based magnetic fluid enhanced the capability of oil seals. The life span of the sealing apparatus composed of mild steel components was remarkably extended due to the high corrosion resistance of ethylene glycol.

陽電荷型磁性凝集核の製造に関する基礎的研究

"Magnetic solid flocculant" (MSF) is a new type flocculant with high magnetic intensity and high positive charge which is useful for the flocculation of fine particles in suspension. The MSF prepared by adsorbing cationic polyelectrolytes to the surface of magnetite particles have abilities to capture fine particles by electrostatic force in a wide pH range and to recover the flocs quickly by magnetic force without changing liquid property. In this study, four kinds of cationic polyelectrolytes are used in preparing MSF and the optimum condition of MSF production is investigated. For all cases, higher pH (especially above pH 7) during polyelectrolytes adsorption gives MSF higher surface potential, and higher polyelectrolyte concentration gives better MSF dispersion. It is observed that three kinds of polyelectrolytes above 300,000 of molecular weight do not detach from a magnetite surface even after several washings. This result indicates that the MSF keeps stable high surface potential and, therefore, can be used repeatedly. Among the four kinds polyelectrolytes used in this study, polyethyleneimine type (molecular weight: 300,000) is the best for MSF production. The optimum condition is as follows; polyelectrolytes concentration: 1,000 ppm, adsorption pH: pH 8, washing after adsorption: 3 times. The MSF produced under optimum condition has large positive potential of around 40 mV in 10-3mol/l NaCl solution in a wide pH range.

INVESTIGATION ON SPIN PINNING EFFECT OF THE MAGNETITE PARTICLE SURFACE COATED WITH ORGANISM

The M?ssbauer spectra of 80 ? magnetite particles before and after coating with the three different organic surfactants were measured. The M?ssbauer spectra after coating appear as dispersion to a different degree with the different organism. When magnetic field (8 kOe) was applied, the superparamagnetic spectra for all sample disappeared and the spectra appeared as sextets. The experimental results showed that the organism produce pinning of the spin of the iron ions on the magnetite particle surface. The depth of pinning with and without applied magnetic field were calculated.

THE EFFECT OF SURFACTANT ON THE MAGNETIC PROPERTIES AND M?SSBAUER SPECTRA OF MEGNETITE

The magnetic properties, infrared absorption spectra and M?ssbauer spectra of dif f irent size magnetite particles were measured before and after coating with organic surfactant. The experimental results show that the nature of coating is chemical absorption between the fine magnetite particle surface and the surfactant. After coating the specific magnetization is reduced under equal magnetic field condition and M?ssbauer spectra become more broadened with the magnetite particle size decreasing. The experimental results may be explained by the surface anisotropy theory.