Manganese Zinc Ferrite Nanoparticles Research Articles

Ultrasonic cavitation induced water in vegetable oil emulsion droplets – A simple and easy technique to synthesize manganese zinc ferrite nanocrystals with improved magnetization

In the present investigation, synthesis of manganese zinc ferrite (Mn 0.5Zn 0.5Fe 2O 4) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn 2+, Zn 2+ and Fe 2+ acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3 h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) techniques. As-prepared ferrite is of 20 nm, whereas the heat treated ferrite shows the size of 33 nm. In addition, magnetic properties of the as-prepared as well as the heat treated ferrites have also been carried out and the results of which show that the spontaneous magnetization ( σ s) of the heat treated sample (24.1 emu/g) is significantly higher than that of the as-synthesized sample (1.81 emu/g). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods; (b) usage of necessary additive components (stabilizers or surfactants, precipitants) and (c) calcination requirements. In addition, rapeseed oil as an oil phase has been used for the first time, replacing the toxic and troublesome organic nonpolar solvents. As a whole, this simple straightforward sonochemical approach results in more phase pure system with improved magnetization.

Preparation of Manganese Zinc Ferrite Nanoparticles by Polymer Matrix Templated Synthesis

MnxZn1-xFe2O4 nanoparticles with x = 0, 0.2, 0.4, 0.5, 0.6 and 1.0 were synthesized by polymer matrix templated synthesis. Ion exchange resins in a form of spherical beads that contained nanopores were used to precipitate the nanoparticles. The synthesized nanoparticles were characterized using several characterization techniques including X-ray diffractometry, transmission electron microscopy and alternating gradient magnetometry. XRD patterns showed that only manganese zinc ferrite nanoparticles were formed. Calculation of crystallite size from x-ray peak broadening showed that the crystallite sizes were within the range 5-11 nm. The crystallite size increased with increasing Mn concentration. TEM images showed that the particles were almost spherical with diameters ranging from 8-19 nm. Magnetization curves passed through the origin and showed no hysteresis indicated that the particles are superparamagnetic. The magnetization value at 10kOe applied magnetic field increased with increasing particle size which was mainly due to the effect of manganese content of the nanoparticles.

Structure of manganese zinc ferrite spinel nanoparticles prepared with co-precipitation in reversed microemulsions

The structure of Mn0.5Zn0.5Fe2O4 spinel ferrite nanoparticles is studied as a function of their size and the experimental conditions of their synthesis using X-ray absorption spectroscopy. The nanoparticles of different sizes down to approximately 2 nm and with a narrow size distribution were synthesized using co-precipitation in reverse microemulsions. Simultaneous refinement of the X-ray absorption fine structure (EXAFS) of three constituting metals shows a migration of Mn and Zn ions to the octahedral site of the spinel lattice compensated by the corresponding migration of the Fe ions. To a smaller extent, Mn ions switch the occupation site already in bulk and in larger nanoparticles, while a sporadic migration of Zn is detected only in the nanoparticles with sizes below approximately 5 nm. X-ray absorption near edge structure (XANES) reveals considerable variations in the position of the Mn K edge, suggesting the average Mn valence in the nanoparticles to be higher than 3+. Annealing at 500 °C relaxes the structure of as-synthesized nanoparticles toward the structure of the ceramic bulk standard.

Transverse susceptibility study of the effect of varying dipolar interactions on anisotropy peaks in a three-dimensional assembly of soft ferrite nanoparticles

Collective magnetization dynamics in nanoparticle assemblies is of current interest as it forms the basis of high density storage media. It is important to understand how interparticle interactions in a three-dimensional (3D) arrangement of superparamagnetic nanoparticles would affect the overall effective magnetic anisotropy of the system. We have studied the influence of varying strengths of dipolar interaction on the static and dynamic magnetic properties of surfactant-coated monodispersed manganese zinc ferrite nanoparticles using reversible transverse susceptibility. We track the evolution of the anisotropy peaks with varying magnetic field, temperature, and interaction strength. The blocking temperature shows an increase from 28 to 32 K and the coercive field (at 10 K) shows an increase from 144 to 192 Oe as the system changes from the case of weakly interacting to strongly interacting 3D assembly of the particles.

Production Scaleup of Reverse Micelle Synthesis

A wide range of techniques for the successful synthesis of nanosized materials have been developed recently. These procedures are sufficient for normal scientific investigation; however, for these materials to be incorporated into any practical application, the process for making them must be scalable to a larger volume. In this work, we focus on a published recipe for manganese zinc ferrite (MZFO) nanoparticles, which uses the reverse micelle synthesis technique. The normal bench-top synthesis has been scaled by a factor of 40 and successfully adapted to a 30-L pilot plant. The product of this synthesis is similar to the bench-top sample, which is also comparable to a ceramic MZFO standard. Through this work, we have demonstrated that the reverse micelle process is scalable to larger volumes.

The preparation of MnZn‐ferrite nanoparticles in a water/CTAB, 1‐butanol/1‐hexanol reverse microemulsion

Manganese zinc ferrite nanoparticles were prepared using a precipitation in reverse microemulsion system consisting of hexadecyltrimethyl ammonium bromide (CTAB) as a surfactant, 1-butanol as a co-surfactant, 1-hexanol as an oil phase and an aqueous solution of metal sulfates. Tetramethyl ammonium hydroxide (TMAH) served as the precipitating agent. The influence of the microemulsion's composition on the nature of the spinel product was studied. The synthesized nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffractometry (XRD), specific surface area (BET) and magnetometry. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Inter-particle interactions and magnetism in manganese–zinc ferrite nanoparticles

Manganese–zinc ferrite (Mn x Zn 1− x Fe 2O 4) nanoparticles were synthesized by reverse micelle technique using two different surfactant media—(1) bis-(2-ethylhexl) sodium sulfosuccinate (AOT) and (2) mix of nonylphenol poly(oxyethylene) 5 and nonylphenol poly(oxyethylene) 9 (NP) followed by annealing of precursors to remove the surfactant coating and to obtain better crystalline phase. A comparison of the magnetic properties showed distinct differences in blocking temperature, coercivity and saturation magnetization. Radio-frequency (RF) transverse susceptibility (TS) measurements were in agreement with the static magnetization data. Our precise TS measurements further revealed features associated with anisotropy fields that were dependent on the grain size, crystallinity and inter-particle interactions. Overall, we have demonstrated that RF TS is an excellent probe of the dynamic magnetization and influence of effects such as crystallinity and inter-particle interactions in soft ferrite nanoparticles.

Magnetic properties of conducting polymer doped with manganese–zinc ferritenanoparticles

The magnetic properties of superparamagnetic particles are influenced by the supporting matrix. Wehave systematically studied the DC magnetic properties of loosely packed manganese–zinc ferrite(Mn0.68Zn0.25Fe2.07O3) nanoparticles synthesized using a reverse micelle technique. The results have beencompared with those for particles suspended in paraffin wax and embedded in a polypyrrolematrix. The polypyrrole-doped particles were prepared using an in situ ultravioletirradiation method and spin-coated into thin films. The loosely packed particlesshowed no resolvable coercivity even well below the blocking temperature. On theother hand, the same particles in wax showed the opening up of a large coercivitybelow the blocking temperature. However, both the samples showed characteristicsuperparamagnetic transition peaks in the temperature-dependent susceptibility nearly atthe same temperature. The particles in the polypyrrole matrix showed a remarkableincrease in the blocking temperature and large hysteresis at 300 K. The structuralcharacterization of the polymer-doped sample showed clustering of the nanoparticles.

Use of multiple-edge refinement of extended x-ray absorption fine structure to determine site occupancy in mixed ferrite nanoparticles

The site occupancy of manganese zinc ferrite (MZFO) nanoparticles is determined by a multiple-edge refinement of the extended x-ray absorption fine structure of the manganese, zinc, and iron absorption edges. The MZFO nanoparticles are generated by a reverse micellar synthetic route and compared to a ceramic standard. The simultaneous fitting of multiple absorption edges to a constrained model is found to yield site occupancies accurate to within eight percentage points.

Variations of melt flow rate and particle size with atomization conditions: H.C. Lee et al (Seoul National University, Seoul, Korea), J Korean Inst of Metals, Vol 30, No 8, 1992, 921–928. (In Korean)

Rare earth (Nd3+) doped Manganese-Zinc Ferrite nanoparticles with composition Mn0.65Zn0.35Fe2-xNdxO4 (x = 0.04, 0.05 and 0.06) were prepared using combustion method of materials preparation. Formation of pure spinel phase was confirmed using X-ray diffraction (XRD) and Fourier transforms infra red spectroscopy (FTIR). The samples were exposed to various doses of γ-radiation (500Gy, 750Gy and 1000Gy) after recording the data on structural and electrical transport properties of as prepared samples, in order to study the effect of γ-radiation on these properties of the nanoparticles. Lattice constant 'a' that showed a moderate increment with Nd3+ doping was found to show a further increase after γ-radiation exposure with nearly a 30%–40% reduction in crystallite size. Transmission electron micrographs showed a decreasing trend of particle size that was nearly proportional to increasing dose of γ-radiation. The samples which showed enhancement in resistivity profile with increasing Nd3+ concentration showed a reverse trend of decrease in the resistivity values with increasing γ radiation dose thus contributing to the conduction process. The dielectric constant of Nd3+ doped samples showed a multifold increase in the dielectric constant with a further increase in its values for radiated samples, when referred to the values reported for undoped Mn-Zn nanoparticle ferrite materials.