Mn Ferrites Research Articles

Impact of metal ions (Cr3+, Co2+, Ni2+, Cu2+ and Zn2+) substitution on the structural, magnetic and catalytic properties of substituted Co–Mn ferrites synthesized by sol–gel route

Manganese substituted cobalt ferrites (CoMn x Fe2−x O4, x = 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized using sol gel autocombustion method were used as photocatalysts for the degradation of both cationic and anionic dyes i.e Safranine-O and Remazol Brilliant yellow. CoMn0.4Fe1.6O4 exhibited maximum photocatalytic activity among all the synthesized ferrites. To further study the effect of metal ion doping on catalytic performance, substitution with different metal ions (Cr3+, Co2+, Ni2+, Cu2+ and Zn2+) was done in CoMn0.4Fe1.6O4 lattice. The structural and magnetic properties of prepared samples were investigated using powder X-ray diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The average crystallite size of the synthesized nanoparticles was observed to be in the range of 39–52 nm. The saturation magnetization of the samples was found to decrease with the introduction of all metal cations (except Co2+) in the Co–Mn lattice. The changes in the catalytic activity were tested for degradation of Safranine-O and Remazol Brilliant yellow. Amongst the synthesized CoMn0.4M x Fe1.6−x O4, Cu substituted Co–Mn ferrite exhibited maximum photocatalytic efficiency. All the magnetic nanoferrites were easily recovered by using an external magnet and could be reused without any remarkable change in catalytic efficiency.

Metal ferrite nanoparticles: Synthesis, characterization, and studies on decontamination of sulfur mustard

Mg, Ca, Mn, Co, Ni, Cu, Zn, Mn-Zn, and Co-Zn metal ferrite and mixed metal ferrite nanoparticles were synthesized by co-precipitation method and were characterized by using transmission electron microscopy, X-ray diffraction, and nitrogen adsorption techniques. Transmission electron microscopy data indicated the formation of metal ferrite and mixed metal ferrite nanoparticles with particle sizes varying from 2 to 88 nm. X-ray diffraction data indicated the formation of metal ferrite and mixed metal ferrite nanoparticles with spinel phase. The metal ferrite nanoparticles were found to be mesoporous and exhibited surface area values in the range of 62–257 m2/g. The ferrite nanoparticles were used in decontaminating sulfur mustard and the reactions exhibited first order behavior. Out of them, Ni, Zn, and Co-Zn ferrite nanoparticles showed greater decontamination efficiency in comparison to other ferrite nanoparticles. While Ni, Zn, and Co-Zn ferrite nanoparticles decontaminated 99.99% of sulfur mustard within 10 h other ferrite nanoparticles took about 16 h to degrade the same. The metal ferrite and mixed metal ferrite nanoparticles degraded toxic sulfur mustard into relatively non toxic products like chloro ethyl vinyl sulfide, hydroxy ethyl vinyl sulfide, hemisulfur mustard, and 1,4-oxathiane. The promising decontamination properties of metal ferrite nanoparticles against sulfur mustard were attributed to the basic sites, Lewis acid sites, and the presence of these sites was confirmed by CO2 and NH3 temperature programmed desorption.

Multi-Elements Doped in Mn-Ferrite by Detonation Method

In the present research, a kind of special emulsions explosive was prepared with taking Ferric nitrate and Manganese nitrate as main oxidants and composite oil as fuel, in which the Magnesium and zinc elements were added and doped in Mn ferrites. The results of which were compared by that of detonation of gas (Hydrogen and oxygen). Results indicated that the detonation products were the same structure, i.e. Jacobsite structure. That is to say, Magnesium and zinc elements were successfully doped in MnFe2O4 crystals. TEM indicated that the powders were spherical and average size was about 20~30nm. The product that obtained by gas detonation was better dispersed and worse uniform than that by explosive. Zn and high content Mg both had great effect on the stability and detonation properties of the explosive, which could produce impurities in detonation products.

Oxide formation during electric resistance welding of low carbon steels

The influence of Mn and Cr on the formation of surface oxides and their entrapment during electric resistance welding of Si containing low carbon steels was studied using thermodynamic calculations and experimental investigation of the microstructure of the different oxide inclusions within welds on electric resistance welding-fabricated pipes. The process of oxidation during the welding process, its dependence on oxygen content, temperature of oxidation and the composition of ferrite within the parent steel were analysed. It was shown that the most important influence on the type of oxide inclusions formed during welding is the Mn/Si ratio, while Cr has an indirect influence via carbide formation, which increases the relative content of Mn in ferrite.

Nickel Substitution Effects on Nano-sized Co, Mn and MnZn Ferrites Synthesized by Sol-gel Method

Nickel substituted nano-sized ferrite powders, Co 1-x Ni x Fe₂O₄, Mn 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ (0.0 ≤ x ≤ 0.2), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in Co 1-x Ni x Fe₂O₄ ferrite but increased for the Mn 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites. For the Co 1-x Ni x Fe₂O₄ and Mn 1-x Ni x Fe₂O₄ (0.0 ≤ x ≤ 0.2) ferrite powders, the Mossbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe 3+ ions. However, the Mossbauer spectrum of Mn 0.8 Zn 0.1 Ni 0.1 Fe₂O₄ consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the Mossbauer spectra could be used to determine the cation distribution equation, and we also explain the variation in the Mossbauer parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the Co 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites but increased in the Mn 1-x Ni x Fe₂O₄ ferrite with nickel substitution. The coercivity decreased in the Co 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites but increased in the Mn 1-x Ni x Fe₂O₄ ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.

Magnetic and structural studies of trivalent Co-substituted Cd–Mn ferrites

Series of polycrystalline Cd0.4Mn0.6CoxFe2−xO4 ferrites, 0≤x≤1, were prepared by solid state reaction method. The samples were characterized by inductive coupling plasma, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectra and vibrating sample magnetometry. This study proved that all samples have single-phase cubic spinel structure. The true lattice constant, saturation magnetization, magnetic moment and trend of grain size and IR band νA showed decrease against x, whereas the trend of crystallite size, threshold frequency, Debye temperature, IR bands ν1 and ν2 and force constants F1 and F2, coercivity, anisotropy constant and residual magnetization showed increase. The IR analysis proved existence of Fe2+, Co2+, Fe4+, Co4+ and/or Mn4+ ions amongst the crystal sublattices. The characteristic bands ν1 and ν2 and force constants F1 and F2 showed decrease versus the tetrahedral- and octahedral-site bond length, respectively. The strain, specific surface area, refractive index, velocity, jump rate and remnant magnetization proved dependence on Co3+ ion content x.

A comparative study of the magnetic and microwave properties of Al3+ and In3+ substituted Mg–Mn ferrites

The effect of substitution of diamagnetic Al3+ and In3+ ions for partial Fe3+ ions in a spinel lattice on the magnetic and microwave properties of magnesium–manganese (Mg–Mn) ferrites has been studied. Three kinds of Mg–Mn based ferrites with compositions of Mg0.9Mn0.1Fe2O4, Mg0.9Mn0.1Al0.1Fe1.9O4, and Mg0.9Mn0.1In0.1Fe1.9O4 were prepared by the solid-state reaction route. Each mixture of high-purity starting materials (oxide powders) in stoichiometric amounts was calcined at 1100°C for 4h, and the debinded green compacts were sintered at 1350°C for 4h. XRD examination confirmed that the sintered ferrite samples had a single-phase cubic spinel structure. The incorporation of Al3+ or In3+ ions in place of Fe3+ ions in Mg–Mn ferrites increased the average particle size, decreased the Curie temperature, and resulted in a broader resonance linewidth as compared to un-substituted Mg–Mn ferrites in the X-band. In this study, the In3+ substituted Mg–Mn ferrites exhibited the highest saturation magnetization of 35.7emu/g, the lowest coercivity of 4.1Oe, and the highest Q×f value of 1050GHz at a frequency of 6.5GHz.

Structural, electrical and magnetic study of nanocrystalline Ti-substituted Zn–Mn ferrospinels

Titanium substituted Zn–Mn ferrites were prepared by sol–gel route. Formation of single phase cubic spinel structure for all the compositions was confirmed from their X-ray diffraction studies. These ferrite samples existed as uniform and homogenous grain size as observed from scanning electron microscopy technique (SEM). The magnetic studies indicated that, the ferrimagnetic behavior increases with titanium substitution. Dielectric constant and complex impedance were measured as a function of frequency in the range 20Hz–1MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell–Wagner type of interfacial polarization and impedance study reveals that the electrical conduction in the ferrites is by the interior of the grain boundaries. In general, the substitution of titanium plays an important role in changing the structural, magnetic and electrical properties of these ferrites.

Structural, electrical, and magnetic properties of polypyrrole–Zn0.5Ni0.45Mn0.05Fe2O4 nanocomposites prepared by in situ chemical polymerization

Polypyrrole–Zn0.5Ni0.45Mn0.05Fe2O4 nanocomposites are conducting polymer-ferrites with useful properties and new functions. The ferrite and polypyrrole–ferrite nanocomposites were synthesized by wow sol gel and in situ chemical polymerization respectively. The structures, morphology, electrical and magnetic properties of the samples were characterized by various instruments. The results of X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectra and field emission scanning electron microscopy (FE-SEM) showed the presence of the two intended phases. FE-SEM results show that phase separation was found to increase with increase of ferrite contents. The crystallite size measured by XRD was found to be in the range 40.9–88.6 nm. Possible bonding effect between metal cations and Polypyrrole (PPy) made the electronic density of the polymer chain reduce and hence resulted in the decrease of the conductivity. The room temperature dielectric measurements were performed in the frequency range 0.1 kHz–1 MHz. The dielectric constant followed the Maxwell–Wagner interfacial polarization. The frequency dependent conductivity obeyed a power law of frequency. Incorporation of ferrites in the conducting polypyrrol matrix leads to higher values of dielectric constant and dielectric loss. The loss tangent was found to have high values for composite materials as compared to pure samples. Under applied magnetic field, the Hysteresis measurements revealed that the saturation magnetization increased with increase in ferrite content. Anisotropy constant K values showed that grains were not single domains and anisotropy contribution is not uniaxial. In general the different variety of the results obtained by just changing the relative percentage of PPy–Zn,Ni,Mn ferrites nanocomposites, made the present studied samples to be useful in radiation absorption and shielding applications.

Ferrites as redox catalysts for chemical looping processes

Spinel ferrites can accommodate oxygen vacancies in their structure and reversibly exchange oxygen with the environment at high temperatures, depending on the partial pressure of oxygen. Therefore their use in Chemical Looping Combustion (CLC) is being studied intensively. In the present work the use of ferrites with the general formula of MeFe2O4 (Me=Mn, Ni, Zn, Co, Cu) as oxygen carriers or potentially reactive supports for oxygen carriers in Chemical Looping Combustion is explored. Polycrystalline ferrite samples are prepared using the conventional ceramic technology of “solid-state reaction”. The performance of the prepared materials is evaluated at a fixed-bed laboratory scale pulse reaction unit. During the fuel oxidation step, methane pulses are injected over the ferrite powder while subsequent oxidation of the solid is performed with gaseous oxygen. The performance of the candidate materials is ranked by comparing the amount of oxygen per mole solid (δ) that can be delivered reversibly to the fuel which corresponds to the Oxygen Transfer Capacity of the different ferrite materials as well as the methane conversion during the fuel oxidation step and the gaseous product distribution. The stability of the materials during multiple reduction–oxidation cycles is evaluated during 5–10 subsequent cycles, each of which is comprised of an activation–regeneration and a solid oxidation step. All the examined ferrites have the ability to deliver their lattice oxygen to a fuel and to some extend regain it in the presence of air. Cu ferrites are very active in CH4 oxidation with maximum conversion higher than 95%, while Zn and Ni ferrites are also highly ranked with methane conversion reaching up to 90% and 78% respectively, however they deactivate very fast after redox cycles. Mn ferrites present relatively low activity (∼30%), while Co ferrites present moderate methane conversion, approximately 68% but remarkable stability during subsequent redox cycles. Cu-, Co- and Ni-ferrites can deliver higher amounts of lattice O, compared to Mn ferrite. The structural and morphological stability of the materials after the multiple redox cycles is examined by X-ray diffraction and SEM–EDS analysis.

Influence of pH on the physical and electromagnetic properties of Mg–Mn ferrite synthesized by a solution combustion method

The synthesis of nano-crystalline Mg–Mn ferrites by a solution combustion method using citric acid and ammonia was investigated by varying the pH of the precursor solution, which played an important role in controlling the morphology of the synthesized powders. The phase formation, microstructure and electromagnetic properties were studied using X-ray diffraction, scanning electron microscopy, impedance analyzer and vibrating sample magnetometer. Single phase pure spinel Mg–Mn ferrite powders were obtained for all the samples at different pH (<1, 3, 5, 7, 9). The results showed that an increase of pH improves the crystallinity of the Mg–Mn ferrite nanoparticles. The average grain size of sintered samples was found to decrease from 2μm to 0.5μm with increasing pH values from pH<1 to pH9, respectively. The dielectric constant of the samples with different pH is in the range of 7–12 from frequencies of 1MHz to 1GHz. The highest saturation magnetization (30.04emu/g) was obtained for the sample with pH<1.

Model Driven Optimization of Magnetic Anisotropy of Exchange-coupled Core-Shell Ferrite Nanoparticles for Maximal Hysteretic Loss.

This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g. size, magnetization, and magnetic anisotropy), and extrinsic properties of the applied fields (e.g. frequency, field strength). Often, the biomedical hyperthermia application limits flexibility in setting of many parameters (e.g. nanoparticle size and mobility, field strength and frequency). We show that core-shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the crystal anisotropy contribution of the Co ferrite phase to the nanoparticles total anisotropy is developed. The experimental results confirm that this framework predicts the hysteretic heating loss correctly when including non-linear effects in an effective susceptibility. Hence, we provide a guide on how to characterize the magnetic anisotropy of core-shell magnetic nanoparticles, model the expected heat loss and therefore, synthesize tuned nanoparticles for a particular biomedical application.

Characterization and Transport Properties of Mixed Ferrite System Mn1-xCuxFe2O4; 0.0 ≤ x ≤ 0.7

A series of Cu-doped Mn ferrites with the formula Mn1-xCuxFe2O4 (0.0 ≤ x ≤ 0.7) were synthesized by citrate auto combustion method. The structural characterization and morphology of the samples were examined by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). XRD and EDX confirmed the formation of single-phase cubic spinel structure. The electrical conductivity (σ), dielectric constant (ϵ′), and dielectric loss factor (ϵ′′) were studied as a function of temperature at different frequencies ranged from 100 kHz to 5 MHz. Increasing is observed in the values of σ, ϵ′, and ϵ′′ with substitution of copper up to x = 0.3. Above this value, a decrease in σ, ϵ′, and ϵ′′ was detected.

Effects of Li+ substitution on the structural and magnetic properties of Co0.5Mn0.5Fe2O4 particles

Co–Mn ferrites with a nominal composition LixCo0.5Mn0.5−xFe2O4 (0.0≤x≤0.3) are prepared by calcining precursor oxalates in air. The effects of composition and calcination temperatures on their structure, morphology, and magnetic properties are studied. A high-crystallized LixCo0.5Mn0.5−xFe2O4 with a cubic structure is obtained when the precursor is calcined at 950°C in air for 3h. All the Li+ substituted Co–Mn ferrites exhibit typical spinel structure. Moreover, lattice parameters of LixCo0.5Mn0.5−xFe2O4 decrease and crystallite size increases with increasing Li+ content, leading to an increase of the specific saturation magnetization and a decrease of the coercive field and the magnetic anisotropy constant.

Kinetics of Solute Partitioning During Intercritical Annealing of a Medium-Mn Steel

The evolution of austenite fraction and solute partitioning (Mn, Al, and C) during intercritical annealing was calculated for a medium-Mn steel containing 11 pct Mn. Austenite growth takes place in three stages. The first stage is growth under non-partitioning local equilibrium (NPLE) controlled by carbon diffusion in ferrite. The second stage is growth under partitioning local equilibrium (PLE) controlled by diffusion of Mn in ferrite. The third stage is shrinkage of austenite under PLE controlled by diffusion of Mn in austenite. During PLE growth, the austenite is progressively enriched in Mn. Compositional spikes evolve early during NPLE growth and broaden with annealing temperature and time.

Nanoferrites: Catalyst for Thermal Decomposition of Ammonium Per Chlorate

Nanoferrite nanoparticles were synthesized by chemical coprecipitation method. The ferrite nanoparticles such as Zn, Mn, Ni, Co, and Cu were prepared. All nanoparticles were characterized by x-ray diffraction and scanning electron microscopy. The average particle of Zn, Mn, Co, Ni and Cu ferrite are 6.8, 2.7, 5.2, 1.1 and 3.9 nm respectively. The effect of ferrite nanoparticles on the thermal decomposition of ammonium per chlorate was studied using thermogravimetic analysis, differential scanning calorimetric (DSC) studies. Activation energy of high temperature decomposition of different alloy nanoparticles was calculated using DSC by Kissinger equation. The catalytic activity of nanoferrites is much sensitive to oxygen and may be effective to improve the thermal decomposition AP-based propellants.

Effect of ZnO on Structural and Magnetic Properties of MnFe2O4/ZnO Nanocomposite

In this paper, we reported a comparative study of structural and magnetic properties of MnFe2O4/ZnO nanocomposite and MnFe2O4 nanoparticles. The samples were prepared with a simple thermal decomposition method and then were characterized through thermogravimetry (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) images, and vibrating sample magnetometry (VSM) at different temperatures. TG curves showed that pure samples can be obtained at 400 °C. XRD pattern of composite sample confirmed coexistence of crystalline cubic spinel Mn–ferrite and hexagonal zinc oxide phases. The estimated lattice parameter of MnFe2O4 nanoparticles, a = 8.39 A, was smaller than bulk value (a = 8.51 A) due to finite size effects. The magnetization of both samples followed the Bloch law with almost the same Bloch constant of β∼ 5 × 10 −5 (K −3/2) showing similar spin wave excitation mechanisms in the samples. However, the VSM measurements indicated that increase of coercivity (H c) of composite sample with decreasing the temperature is faster when compared with pure ferrite.

Dielectric Behavior and Magnetic Properties of Mn-Substituted Ni–Zn Ferrites

Nanocrystalline spinel ferrites of nominal stoichiometry Ni0.5Zn0.5Mn x Fe2−x O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by chemical co-precipitation. X-ray diffraction analysis revealed formation of a single cubic phase with no metal oxide secondary phase; increased intensity of peaks of the doped samples suggests that, in the range studied, substituents are completely dissolved in the cubic lattice. Grain size was measured by scanning electron microscopy, by use of the line intercept method. Dielectric measurements were obtained as a function of frequency in the range 20 Hz to 3 MHz. It was found that hopping conduction was the predominant mechanism of conduction in frequency-dependent alternating current conductivity. Conductivity relaxation of the charge carriers was examined by use of the electrical modulus formalism; the results were indicative of the presence of the non-Debye-type relaxation in the ferrites. The grain boundary contribution was clearly apparent from Cole–Cole plots. Hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicative of the superparamagnetic nature of these samples. On the basis of these sample characteristics it is suggested that Ni–Zn–Mn ferrites may be potential candidates for hyperthermia applications.

Study on the structural and electromagnetic properties of Tm-substituted Mg–Mn ferrites by a solution combustion method

The effect of thulium ion substitution for iron on the structural and electromagnetic properties of Mg–Mn ferrites is reported. The Mg0.9Mn0.1TmxFe1.8−xO4 ferrite compositions with x=0.0, 0.025, 0.05, and 0.075 were synthesized by a nitrate–citrate solution combustion method. Tm substitution had taken place and this was found to produce a secondary phase TmFeO3. The crystallite size of the powder calcined at 500°C was in the range of 9–13nm. Subsequently, the calcined ferrite powders were compacted and sintered at 1250°C. It was found that the physical and magnetic properties had changed with Tm contents. Bulk density was found to decrease from 4.26 to 3.82g/cm3 with increasing Tm contents. It was also found that the saturation magnetization (Ms=38.41–23.62emu/g) had decreased with an increase of Tm. In this study, the highest resistivity (39.84×106Ωcm) was observed for Mg0.9Mn0.1Fe1.725Tm0.075O4. The correlation between structural and electromagnetic properties of the Tm-substituted samples is interpreted based on phase composition as well as microstructure.

Preparation of Zn–Mn ferrite from spent Zn–Mn batteries using a novel multi-step process of bioleaching and co-precipitation and boiling reflux

Synthesis of wide-application Zn–Mn ferrite soft magnetic materials using spent Zn–Mn batteries as starting raw materials has attained growing attentions in recent years. The multi-step series processes of reductive acid leaching and oxidative co-precipitation and high temperature calcination or hydrothermal reaction were generally utilized to carry out the conversion. In this work, a novel multi-step process of bioleaching and co-precipitation at 30°C and boiling reflux at 100°C, which was characteristic of low cost, environmental friendliness and energy saving, was attempted to accomplish the conversion for the first time. The results showed that synthesis of Zn–Mn ferrite using bioleaching liquor as a precursor was feasible. NaOH was the best coprecipitator for manufacturing the soft magnetic material from bioleaching liquor compared with NaHCO3 and NH4HCO3. Higher pH value of the second co-precipitation at 13.0, higher total concentration of Mn2++Zn2++Fe2+ at 2.0mol/l and longer reflux time at 5h were essential for greater magnetization and better crystallinity. Under optimum conditions, this novel multi-step process harvested soft magnetic material with highest saturation magnetization of 102emu·g−1, offering an alternative to convert spent Zn–Mn batteries into Zn–Mn ferrite.