Manganese Ferrite Particles Research Articles

Suspension rheology of polyaniline coated manganese ferrite particles under electric/magnetic fields

Manganese ferrite (MnFe2O4) nanoparticles initially fabricated using a solvothermal process were coated with conducting polyaniline (PANI) to produce core/shell-structured MnFe2O4/PANI nanoparticles. An electro/magnetorheological (E/MR) fluid was prepared by suspending MnFe2O4/PANI particles in silicone oil, and the rheological properties under either electric or magnetic fields were investigated. Scanning electron microscope and transmission electron microscope provided the particle morphology and size information. X-ray diffraction and Fourier transform infrared spectroscopy were used to analyze the crystal structure and chemical composition of the particles. Chain formation in E/MR fluids under electric or magnetic fields was observed by optical microscopy, and the rheological properties were evaluated using a rheometer. Steady shear and dynamic oscillatory tests were conducted to confirm the effective E/MR characteristics while varying the electric/magnetic field strength. The dielectric properties of the particles measured using an LCR meter were analyzed based on the Cole-Cole model. The E/MR fluids composed of MnFe2O4/PANI showed a reversible and fast electro/magnetic response.

Effects of synthesis conditions on structure and magnetic properties of MnFe2O4particles

Manganese ferrite (MnFe2O4) nanoparticles were synthesized through a coprecipitation method using manganese (II) chloride tetrahydrate (MnCl2·4H2O) and ferric chloride hexahydrate (FeCl3·6H2O) as precursors. The scanning electron microscopy images showed that the as-synthesized particles were granular and about 20 nm. The X-ray diffraction patterns revealed that the manganese ferrite phase was completely decomposed into ferric oxide (Fe2O3) and manganese (III) oxide (Mn2O3) after annealing above 800°C in air. In contrast, its crystalline quality significantly improved when it was annealed in argon. By using the vibrating-sample magnetometry technique, it was demonstrated that the saturation magnetization (Ms) of the as-prepared sample (~36.6 emu/g) decreased sharply up to ~5 emu/g after annealing at 1000°C in air and significantly increased to ~77.6 emu/g when it was annealed at 1000°C in argon. Under sunlight radiation, a higher efficiency was observed for manganese ferrite particles annealed in argon in the presence of hydrogen peroxide (H2O2), mainly due to the Fenton reaction between manganese ferrite and hydrogen peroxide. The authors suggest that the presence of hydrogen peroxide and the enhancement of the crystalline quality of the manganese ferrite phase are the two leading factors in improving methylene blue degradation efficiency.

Recovery of Neodymium (III) from Aqueous Phase by Chitosan-Manganese-Ferrite Magnetic Beads.

Neodymium is a key rare-earth element applied to modern devices. The purpose of this study is the development of a hybrid biomaterial based on chitosan (CS) and manganese ferrite (MF) for the recovery of Nd(III) ions from the aqueous phase. The preparation of the beads was performed in two stages; first, MF particles were obtained by the assessment of three temperatures during the co-precipitation synthesis, and the best nano-MF crystallites were incorporated into CS to obtain the hybrid composite material (CS-MF). The materials were characterized by FTIR, XRD, magnetization measurements, and SEM-EDX. The adsorption experiments included pH study, equilibrium study, kinetics study, and sorption–desorption reusability tests. The results showed that for MF synthesis, 60 °C is an appropriate temperature to obtain MF crystals of ~30 nm with suitable magnetic properties. The final magnetic CS-MF beads perform maximum adsorption at pH 4 with a maximum adsorption capacity of 44.29 mg/g. Moreover, the material can be used for up to four adsorption–desorption cycles. The incorporation of MF improves the sorption capacity of the neat chitosan. Additionally, the magnetic properties enable its easy separation from aqueous solutions for further use. The material obtained represents an enhanced magnetic hybrid adsorbent that can be applied to recover Nd(III) from aqueous solutions.

Behavior of nanocomposite consisting of manganese ferrite particles and atomic layer deposited bismuth oxide chloride film

Nanocomposites of manganese ferrite and bismuth oxide chloride were synthesized. The composites consisted of 10 nm thick nanocrystalline bismuth oxide chloride thin film grown by atomic layer deposition on spinel MnFe2O4 nanoparticles prepared by wet chemical synthesis. The composite layers exhibited nonlinear polarization behavior in both magnetic and electric fields at room temperature. The magnetic coercive force, HC, was 30–40 Oe at room temperature. The width of electrical charge – voltage hysteresis loop reached 3.6 MV/cm.

Study the spin configuration and the saturation magnetization of manganese-zinc ferrite nanoparticles by the Monte Carlo method

In this work, the simulations of magnetic properties of nano-sized manganese ferrite particles with zinc replacement were performed. The percentage of replacement laid in range from 0% to 80%. The parameters of particles, including exchange integrals, were taken from experimental data received for MnxZn1-xFe2O4. The sizes of particles and thickness of defective surface layer were taken, taking into account real sizes distribution for manganese nanoparticles received by the way of mechanochemical synthesis. Simulations were performed using the Monte-Carlo methods, Metropolis algorithm.

A Monte Carlo Simulation of the Spin Configuration of Manganese Ferrite Nanoparticles

A simulation of magnetic properties of nanosized manganese ferrite particles is performed. In the simulations, the Metropolis Monte Carlo algorithm is used. The particle parameters are selected taking into account true values of the exchange integrals and anisotropy constants, as well as particle size distribution in nanostructured manganese ferrite powder produced by the mechanochemical synthesis.

Investigation of the thermal stability of Mn ferrite particles synthesized by a modified co-precipitation method

Manganese ferrite particles with spinel structure were synthesized by a modified co-precipitation method, and then the thermal stability on their structural and magnetic properties was investigated by thermal annealing at different gas ambients. Experimental results showed that decomposition of metal oxides occurred when Mn ferrite particles with spinel structure were annealed under air ambient, while samples annealed in vacuum or argon remained in the spinel structural form. The highest saturation magnetization value of 58 emu/g was obtained when the sample was annealed at 400°C in argon. The result showed that the thermal stability of MnFe2O4 was better under Ar ambient conditions or in vacuum.

Magnetic polyvinylamine nanoparticles by in situ precipitation reaction

Magnetic nanoparticles represent emerging tools in biomedical and pharmaceutical research. Because in most cases, the surfaces of these nanoparticles are hydrophobic, surface modifiers are usually applied to stabilize the colloidal suspension in an aqueous media. This investigation reports a simple technique for the preparation of MnFe2O4 synthesized within polyvinylamine (PVAm) nanoparticle reactors. Magnetite nanoparticles were previously synthesized using a similar scheme; however, substituting MnFe2O4 for Fe3O4 improved nanoparticle magnetization properties and further established the synthetic approach. PVAm nanoparticles exhibited more than 18% manganese ferrite loading by weight, a saturation magnetization of ∼ 40 emu/g of MnFe2O4, excellent colloidal stability, and reactive primary amines for possible drug conjugation or surface modification. Transmission electron micrographs revealed that the dispersions contained ∼ 50 nm PVAm nanoparticles incorporating manganese ferrite particles with a size less than ∼ 7 nm. This reaction scheme further justifies a unique synthetic methodology for magnetic nanoparticles offering potential use in contrast-enhanced magnetic resonance imaging or drug delivery. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 991–996, 2010

Influence of magnetic anisotropy constant and particle domain magnetization on magneto-dielectric response of substituted manganese ferrite particles dispersed in kerosene

This paper presents a dielectric and magneto-dielectric study of magnetic fluids made of three different, partially substituted, manganese ferrite particles dispersed in kerosene. Measurements were performed using a wholly automated spectrometer in the frequency range 1 mHz–10 MHz and a temperature range from −200°C up to 100°C. We can distinguish the two phases (solid and liquid) in pure kerosene and three phases for all the magnetic fluid samples. We observed the effect of anisotropy constant and domain magnetization of the particles on magneto-dielectric measurements. We also observed the temperature sensitivity of these fluids.

Dynamic properties of colloidal suspensions of manganese ferrite particles

Measurement of the magnetic field dependence of the complex susceptibility, /spl omega/)=/spl chi/'(/spl omega/)-i/spl chi/(/spl omega/), of four colloidal suspension of Mn/sub x/Fe/sub 1-x/Fe/sub 2/O/sub 4/ particles in isopar M has enabled the dependence on x of anisotropy constant, K, internal field, H/sub A/, magnetogyric ratio, /spl gamma/, and resonant frequency, f/sub res/, to be determined. For x having values of 0.1, 0.3, 0.5 and 0.7, H/sub A/ has average values of 40, 35, 40 and 49 kA m/sup -1/, whilst /spl gamma/ has corresponding values of 2.36, 2.48, 2.43 and 2.4 10/sup 5/ s/sup -1/ A/sup -1/ m, respectively.

Broad-band measurement of the complex susceptibility of magnetic fluids

The authors report on the measurement, over the frequency range 10 Hz to 3 GHz, of the complex susceptibility, chi ( omega )= chi '( omega )-i chi "( omega ), of a magnetic fluid with manganese ferrite particles of median diameter 9.4 nm in a hydrocarbon carrier. This upper frequency was realized by use of a HP Network Analyser which operates over the frequency range 300 kHz to 3 GHz and has enabled a more complete susceptibility-frequency profile to be determined. The presence of a loss-peak at 30 MHz in the chi "( omega ) component is a demonstration of the phenomenon of superparamagnetism in small ferromagnetic particles whilst the transition of chi '( omega ) to a negative value at 65 MHz is indicative of ferroresonance.

Preparation of manganese ferrite fine particles from aqueous solution

Fine manganese ferrite particles have been prepared by a coprecipitation method and subsequent digestion process (below 100°C). Manganous salts mixed with either ferric or ferrous salts were coprecipitated with sodium hydroxide. Particles produced from ferric salts were MnFe 2O 4 with relatively smaller sizes (5 to 25 nm) while ferrous salts created Mn x Fe 3− x O 4 (0.2 < × < 0.7) with bigger sizes up to 180 nm. In either case, the particle size appeared to be a unique function of the ratio of metal ion concentration to hydroxide ion concentration when the digestion conditions were fixed. For the system with ferric salts, the undigested samples were polycrystals with crystallite sizes of about 2 nm. Digestion, which could be described as an Ostwald ripening process, did not change the crystalline structure but increased both the crystallite size and the particle size. A basic solution was essential for an effective digestion process in this system. The system with ferrous salts, on the contrary, needed an acidic solution to create a single ferrite phase. Digestion changed both the crystalline structure and the particle size of the precipitated precursors. This process involved a dissolution and renucleation/growth mechanism. Cation and anion effects on the particle size and the evolution during digestion were also studied.

DISTRIBUTION OF MANGANESE IN MANGANESE FERRITE PARTICLES PREPARED BY AIR OXIDATION OF HYDROXIDE SUSPENSIONS

Abstract The distribution of manganese in manganese ferrite particles prepared by the air oxidation of coprecipitated hydroxide suspensions has been investigated from the dissolution curves by using the core-model. The mole fraction of manganese increases gradually from the center to the surface of the particles and also increases abruptly near the particle surface.