MnFe2O4 Sample Research Articles

Finding the best frequency dependent performance of 3d transition metals (Co, Ni, and Mn) substituted nano magnetite for miniaturizing device applications

Ferrite samples with enhanced magneto-dielectric properties are more essential in electromagnetic applications. Therefore, a parent composition of Fe3O4 has been modified by substituting 3d transition metal elements (Co, Ni, Mn) at a single Fe atom using the co-precipitation synthesis method. The structural properties of the synthesized Fe3O4, NiFe2O4, CoFe2O4, and MnFe2O4 samples have been evaluated from the X-ray diffraction patterns. The surface morphology and microstructures of the studied samples were studied by field emission scanning electron microscopy and the average grain size of all the studied samples varied from 60.11 to 106.03 nm. The magneto-dielectric properties were analyzed by frequency dependent permeability (μ) and permittivity (ε) measurements for the range of 100 Hz to 100 MHz. The conduction process for the synthesized ferrites has been noticed from the ac conductivity (σac). The localized relaxation mechanism for the studied ferrites has been observed from the variation of imaginary portion of the electric modulus (M") and the impedance (Z"). Moreover, the mismatch (Z/ηο) between the impedance of the antenna substrates (Z) made of the studied samples and air (ηο) has been evaluated from the permeability and permittivity. Finally, NiFe2O4 has been derived as a suitable ferrite for miniaturizing devices over a frequency range of 10 kHz-6.5 MHz.

Structural, optical, magnetic properties and energy-band structure of MFe2O4 (M = Co, Fe, Mn) nanoferrites prepared by co-precipitation technique.

MFe2O4 (M = Co, Fe, Mn) nanoparticles were successfully formed through the chemical co-precipitation technique. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis were used to investigate samples' structural properties. The investigated structural properties included phases formed, crystallite size, cation distribution, hopping length, bond length, bond angle, edge length, and shared and unshared octahedral edge length. Scanning electron micrographs of the prepared samples demonstrated well-defined crystalline nanoparticles. The grain diameter was 15, 9, and 34 nm for CoFe2O4, Fe3O4, and MnFe2O4, respectively. The energy-dispersive X-ray analysis confirmed the existence of every element (Co, Fe, and O) and no discernible impurities in the samples. The optical properties were studied in detail through photoluminescence (PL) spectroscopy and Raman spectroscopy. The presence of active modes in Raman spectra confirmed the spinel structure of the MFe2O4 nanoparticles. The direct bandgap energy estimated through UV-visible spectroscopy was about 2.59-2.64 eV, corresponding with the energy-band structures of the octahedral site (1.70 eV) and the tetrahedral site (0.9 eV). This result was further confirmed by PL emission spectra. Based on Mie theory and UV-visible and PL spectral data, the mechanism of photothermal characterization for MFe2O4 nanoparticles was determined. Investigating the changes in temperature of magnetic parameters including coercivity, squareness ratio, and saturation magnetization for MFe2O4 samples showed the dominant influence of ion distribution and A-A, A-B, and B-B exchange interactions. This study also showed that strong anisotropy and weak dipolar interaction tended to increase the coercivity and squareness ratio of CoFe2O4. Conversely, weaker anisotropy and stronger dipolar interaction corresponded with the small coercivity and squareness ratio of Fe3O4 and MnFe2O4 samples.

Preparation and characterization of MnFe2O4 by a microwave-assisted oxidative roasting process

An innovative and effective technological process is proposed to synthetize spinel manganese ferrite (MnFe2O4) by a microwave-assisted oxidization roasting process. In the current paper, the effect of operating variables on the formation mechanism of Fe-MnO systems for synthesizing spinel MnFe2O4 is initially investigated to reveal the oxidation mechanism and phase transformation during the microwave–assisted oxidative roasting process. The synthetic MnFe2O4 microparticles with a saturation magnetization (Ms) of 70.5 emu/g, a coercivity (Hc) of 4.65 Oe and a ratio of the saturation magnetization to remanent magnetization (Ms/Mr) of 0.055 were successfully prepared by heating for 30 min at 1000 °C in an air atmosphere. The MnFe2O4 samples exhibited normal and inverse spinel crystal structures, inevitably coexisting and co-transforming simultaneously at high temperature (≥950 °C). Furthermore, this innovative and effective technological process can be extended to fabricate other spinel ferrite particles of interest.

Morphological design of MnFe2O4 facets (cube, flakes and capsules) for their role in electrical, magnetic and photocatalytic activity

The present work describes the effect of three different morphologies of the spinel ferrite MnFe2O4 and their facet-oriented growth on the physical, electrical, magnetic, and photocatalytic activity of an organic pollutant. The solvothermally synthesized MnFe2O4 samples revealed a cubical, flake, and capsule morphology, and their structural entities were confirmed through various physico-chemical characterizations. The mechanistic insights on the efficiency of the nanomorphologies from the different physical studies were given preference above the extent of the outcomes. The optical studies through UV spectroscopy revealed the capsule morphology having the least bandgap of 2.05 eV, whereas the electrical studies revealed that the cubical morphology of MnFe2O4 exhibited the highest electrical conductivity of 5.34247 × 10−7 S cm−1 at room temperature. The magnetic studies were carried out in a Vibrating sample magnetometer (VSM) which exposed the highest magnetic saturation for the capsule sample with 35.9 emu g − 1 with the least Yafet-Kittel angle of 88.79. The photocatalytic studies with methylene blue as the organic pollutant demonstrated that the flake morphology of MnFe2O4 provided an enhanced efficiency of 98% and stability up to four consecutive cycles compared to the other two morphologies. In this work, the mechanism behind the superior performance of each nanomorph of the MnFe2O4 ferrite in the respective electrical, magnetic and photocatalytic activity is explained in brief which could be utilized for tuning the morphologies of other ferrites to suit the specific applications.

Enhancing the Liquefied Petroleum Gas Sensing Sensitivity of Mn-Ferrite with Vanadium Doping

Mn-Ferrite with a nanostructure is a highly valuable material in various technological fields, such as electronics, catalysis, and sensors. The proposed article presents the hydrothermal synthesis of Mn-ferrite doped with V (V) ions. The range of the doping level was from 0.0 to x to 0.20. The fluctuation in tetrahedral and octahedral site occupancies with Fe (III), Mn (II), and V (V) ions was coupled to the variation in unit cell dimensions, saturation magnetization, and LPG sensing sensitivity. The total magnetic moment shows a slow decrease with V-doping up to x = 0.1 (Ms = 51.034 emu/g), then sharply decreases with x = 0.2 (Ms = 34.789 emu/g). The dimension of the unit cell increases as x goes up to x = 0.1, then lowers to x = 0.2. As the level of V (V) ion substitution increases, the microstrain (ε) also begins to rise. The ε of a pure MnFe2O4 sample is 3.4 × 10−5, whereas for MnFe2−1.67 xVxO4 (x = 0.2) it increases to 28.5 × 10−5. The differential in ionic sizes between V (V) and Fe (III) and the generation of cation vacancies contribute to the increase in ε. The latter is created when a V (V) ion replaces 1.6 Fe (III) ions. V-doped MnFe2O4 displays improved gas-sensing ability compared to MnFe2O4 at lower operating temperature. The maximum sensing efficiency was observed for 2 wt% V-doped MnFe2O4 at a 200 °C optimum operating temperature.

Mechanistic insights into the sol-gel synthesis of complex (quaternary) Co–Mn–Zn-spinel ferrites: An annealing dependent study

Synthesis conditions, cation distribution at tetrahedral and octahedral sites and their stability play very important roles in controlling phase-purity and physicochemical properties of spinel ferrite compounds. In this work, an attempt is made to understand how the progress of phase-formation and the structural and magnetic properties are influenced by the annealing temperature and nature of cations used in the synthesis of quaternary spinel ferrite ceramics. A series of Co0.8-xMn0.2ZnxFe2O4 (x = 0, 0.2, 0.4, 0.6 and 0.8) (CMZF) spinel ferrite samples were synthesized by citric acid assisted sol-gel technique followed by annealing at 400, 600 and 800 °C. To compare the progress of phase formation/stability of the cations, simple (binary) spinel ferrite reference samples, such as CoFe2O4, MnFe2O4 and ZnFe2O4, were also synthesized by the same technique and are calcined at the same conditions. In case of CoFe2O4, all the samples have single phase spinel structure, but a transformation from an inverse spinel-type to nearly normal spinel ferrite-type cation distribution is observed with increasing annealing temperature. The as-prepared MnFe2O4 sample and that annealed at 400 °C show formation of single phase spinel ferrite, while those annealed at 600 and 800 °C decomposes completely into Mn2O3, α-Fe2O3 and amorphous-FeO phases. In contrast, for ZnFe2O4 samples, a transformation from the ZnO and α-Fe2O3 phases (present in the as-prepared and up to 600 °C annealed samples) to pure ZnFe2O4–phase occurs only at/above 800 °C. Interestingly, our results show that the progress of the phase formation behavior of the CMZF samples can be predominantly considered as a combination of the behavior and energetics typically exhibited by the individual (simple) ferrite systems. Overall, our work provides the necessary impetus for achieving the phase purity and required physicochemical properties of complex ferrite systems by choosing the cations suitably, based on their nature and annealing behavior.

Synthesis and magnetism property of manganese ferrite MnFe2O4 by selective reduction and oxidization roasting process

A selective reduction followed by an oxidization roasting process has been reported as an effective route to synthetize spinel manganese ferrite (MnFe2O4). In the current work, during the selective reduction process, the FeyMn1−yO (0 ≤ y ≤ 1) samples that acted as intermediates for synthesizing MnFe2O4 were successfully synthesized from Fe2O3 and Mn2O3 systems. The y-value in the synthetic FeyMn1−yO sample was in the range of 0–1 at 800 °C after 30 min. Next, during the oxidization roasting process, the synthetic MnFe2O4 micro-particles with saturation magnetization of 73.7 emu/g were successfully prepared from the FeyMn1−yO samples by an oxidization roasting process for 30 min at 1000 °C in air atmosphere. The formation mechanism and interfacial reaction of manganese ferrite spinel MnFe2O4 samples were systematically investigated by SEM/EDS, XRD, XPS and VSM. Under low temperature (<950 °C), the main reactions were the oxidization of FeyMn1−yO to MnxFe3−xO4 (1 < x ≤ 3), MnxFe3−xO4 (0 < x < 1) and Fe2O3. Under high temperature (>1000 °C), the MnyFe1−yO sample was oxidized to the MnFe2O4 sample, and the normal and inverse spinel structures of MnFe2O4 samples inevitably coexisted and were co-transformed at the same time. This study reported a simple synthetic route that combined selective reduction with an oxidization roasting method to successfully synthesize MnFe2O4 micro-particles. Furthermore, this method could be extended to fabricate other spinel ferrite particles of interest.

Chitosan coating by mechanical milling of MnFe2O4 and Mn0.5Co0.5Fe2O4: Effect of milling

Manganese ferrite (MnFe2O4) and manganese-cobalt ferrite (Mn0.5Co0.5Fe2O4) fine powders were produced by glycol-thermal technique. Fine powders were then milled with chitosan for different times ranging from 5 hours to 60 hours. XRD patterns of the as-prepared and milled oxides confirm cubic phase structure with an average crystallite size of 11 nm. The observed values of lattice parameter decrease with milling due to the inversion of cations induced by milling. TEM results reveal nanoparticles with spherical shape and average particle sizes correlating to XRD data. No aggregation of particles was observed after milling suggesting effective chitosan coating. Magnetization studies performed at room temperature in fields up to 14 kOe revealed the superparamagnetic nature of both naked and coated nanoparticles with spontaneous and saturation magnetizations decreasing with milling. Larger coercive fields observed in Mn-Co oxides were attributed to higher magnetic anisotropy associated with Co ions. A reduction of coercive field due to milling duration was observed. 57Fe Mössbauer spectra of Mn0.5Co0.5Fe2O4 samples show ordered magnetic states, while paramagnetic nature is revealed in MnFe2O4 samples. Hence, current results suggest that chitosan coating can be successfully achieved through mechanical milling resulting in nanoparticles with potential for biomedical applications. The differences in the magnetic properties of the samples are discussed based on Stoner-Wohlfarth theory.

Composition dependent structural and morphological modifications in nanocrystalline Mn-Zn ferrites induced by high energy γ-irradiation

We report the high energy γ-irradiation induced structural transformations in nanocrystalline Mn1-xZnxFe2O4 (x = 0, 0.25, 0.5, 0.75 and 1) samples synthesized by solution combustion method using a mixture of fuels. All samples were exposed to a gamma radiation dose of 50 kGy. The γ-irradiation decomposes the single phase cubic spinel (Fd-3m) structure of the samples into new stable phases. The pure MnFe2O4 sample transformed to Mn2O3 and Fe1-xO phases whereas the pure ZnFe2O4 sample retained its phase. For the samples with intermediate Zn-content γ-irradiation facilitates the formation of stable α-Fe2O3 and ZnFe2O4 phases, along with amorphous MnO phase. The scanning electron micrographs demonstrate the complete change of the sample morphology with fusion of the particles after γ-irradiation. Our results are important for the understanding of the stability and performance of the devices used in various technological applications near intense high energy radiation sources.

Comparative Study of MnFe2 O 4 Nanoparticles Synthesized by Sol-gel Method with Two Different Surfactants

Nanoparticles (NP) of MnFe2O4 were synthesized via sol-gel method, with calcination process at 600 °C. The effects of different surfactants namely polypropylene glycol (PPG) and polysorbate 80 (PS80) in the formation of crystal structure, magnetic properties, and optical properties were studied using X-ray diffraction (XRD), vibration sample magnetometry, UV-visible diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Brunauer-Emmett-Teller (BET) surface area test was also performed. XRD investigations revealed that MnFe2O4 sample synthesized using PS80 as surfactant (sample 2) showed pure crystalline phase of a cubic spinel structure whereas sample synthesized with PPG (sample 1) exhibited an additional phase of α-Fe2O3. The morphology of the samples was recorded using a scanning electron microscope (SEM). Energy dispersive X-ray (EDX) results showed that the composition of the elements was as relevant as expected from the sol-gel method. The magnetic hysteresis loops confirmed the super-paramagnetic behavior of both the samples. PL studies revealed a sharp narrow band green emission exhibited by both the samples. Catalytic activity of MnFe2O4 nanoparticles (NPs) was performed. The catalysts MnFe2O4, samples 1 and 2, were tested for the oxidation of benzyl alcohol to benzaldehyde. The conversion of benzyl alcohol reached a maximum of 82.45 % for MnFe2O4 sample 2, whereas for sample 1, the conversion was only 68.52 %. These Mn ferrite samples have potential applications in LED or laser diodes.

Influences of morphology and structure on Mn-based multi-step thermochemical H2O splitting cycle

The multi-step thermochemical water splitting cycle based on MnFe2O4–Na2CO3 has emerged as an attractive process due to its relatively low reaction temperature. The main challenges are how to enhance its H2/O2 release rates and capacities. Herein, a series of MnFe2O4 with different microstructures synthesized by hydrothermal method were tested in H2O splitting reaction. It was found that MnFe2O4 samples with smaller particle size and fine crystallinity exhibited higher H2 production which was benefit from enhanced intimate contact between homogeneous particles and better ionic transport within fine crystals. In order to enhance the reaction kinetics of the O2 release reaction, a hydrolysis treatment was introduced to the multi-step cycle. As a result, the lamellar structure of Na+ extracted Na1−x(Mn1/3Fe2/3)O2 oxide became unstable and collapsed into cubic MnFe2O4 spinel structure more easily under heating, a structure characteristic suitable for O2 release reaction. Compared to direct O2 release reaction between layered Na(Mn1/3Fe2/3)O2 oxide and CO2, the hydrolysis treatment lead to much faster reaction rate.

Photocatalytic reduction of chromate oxyanions on MMnFe2O4 (M=Zn, Cd) nanoparticles

Spinel MxMn1−xFe2O4 ferrites (M=Zn or Cd) synthesized via the co-precipitation method were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV–vis and Mössbauer spectroscopy. MnFe2O4 exhibited mainly cubic structure when Cd was incorporated, whereas the Zn incorporation stimulated a mixed phase consisting of MnFe2O4 and ZnMnFe2O4. The IR spectra of both Cd- and Zn modified MnFe2O4 samples revealed vibration of the chemical bond Fe2+O2− in A location of the tetrahedron which infers that dopants were uniformly distributed over the system. The optical band gap energy showed large variations; a smaller value was determined for Cd0.2Mn0.8Fe2O4 (1.46eV) when compared with those of MnFe2O4 (2.16eV) and Zn0.2Mn0.8Fe2O4 (2.8eV). The analysis of Mössbauer spectra gave inversion values of Fe3+ distribution in tetrahedral coordinated sites of 24%, 57% and 65% in MnFe2O4, Zn0.2Mn0.8Fe2O4 and Cd0.2Mn0.8Fe2O4, respectively. It was found that Cd0.2Mn0.8Fe2O4 exhibited the best performance in the photocatalytic reduction of Cr(VI) to Cr(III) having a maximum value of 96% within 30min, and the experimental data obeyed pseudo-second-order rate kinetic model. Also, the linear model of Langmuir attained a maximum adsorption capacity of 37mgg−1 for Cd0.2Mn0.8Fe2O4.

The influence of reactive milling on the structure and magnetic properties of nanocrystalline MnFe2O4

Abstract Nanocrystalline manganese ferrites (MnFe2O4) have been synthesized by direct milling of metallic manganese (Mn) and iron (Fe) powders in distilled water (H2O). In order to overcome the limitation of wet milling, dry milling procedure has also been utilized to reduce crystallite size. The effects of milling time on the formation and crystallite size of wet milled MnFe2O4 nanoparticles have been investigated. It has been observed that single phase 18.4 nm nanocrystalline MnFe2O4 is obtained after 24 h milling at 400 rpm. Further milling caused deformation of the structure as well as increased crystallite size. With the aim of reducing the crystallite size of 18.4 nm, MnFe2O4 sample dry milling has been implemented for 2 and 4 h at 300 rpm. As a result, the crystallite size has been reduced to 12.4 and 8.7 nm, respectively. Effects of the crystalline sizes on magnetic properties were also investigated. Magnetization results clearly demonstrated that crystallite size has much more effect on the magnetic properties than average particle size.

Significantly Improved Dehydrogenation of LiAlH4 Destabilized by MnFe2O4 Nanoparticles

The effects of nanosized MnFe2O4 additive on the dehydrogenation properties of LiAlH4 prepared by ball milling were investigated for the first time. It was found that the LiAlH4 + 7 mol % MnFe2O4 sample started to decompose at 62 and 119 °C for the first two dehydrogenation stages and released 7.45 wt % hydrogen, which is 88 and 71 °C lower than those of as-received LiAlH4, respectively. The isothermal dehydriding kinetics show that the doped LiAlH4 sample could release about 4.7 wt % hydrogen in 70 min at 90 °C. Furthermore, the first two dehydrogenation steps could be finished within 80 min with 7.44 wt % hydrogen released at 120 °C, whereas as-received LiAlH4 only released about 0.5 wt % hydrogen for the same temperature and time. From differential scanning calorimetry (DSC) and Kissinger desorption kinetics analyses, the apparent activation energies, Ea, of the doped sample were 66.7 kJ/mol for the first dehydrogenation stage and 75.8 kJ/mol for the second dehydrogenation stage, resulting in decreases...

Characterization of Stoichiometric Nanocrystalline Spinel Ferrites Dispersed on Porous Silica Aerogel

Stoichiometric magnetic nanosized ferrites MFe2O4 (M = Mn, Co, Ni) were prepared in form of nearly spherical nanocrystals supported on a highly porous silica aerogel matrix, by a sol-gel procedure. X-ray diffraction and transmission electron microscopy indicate that these materials are made out of non-agglomerated ferrite nanocrystals having size in the 5-10 nm range. Investigation by Mössbauer Spectroscopy was used to gain insights on the superparamagnetic relaxation and on the inversion degree. Magnetic ordering at room temperature varies from superparamagnetic in the NiFe2O4 sample, highly blocked (approximately 70%) in the MnFe2O4 sample and nearly fully blocked in the CoFe2O4 sample. A fitting procedure of the Mössbauer data has been used in order to resolve the spectrum into the tetrahedral and octahedral components; in this way, an inversion degree of 0.68 (very close to bulk values) was obtained for 6 nm silica-supported CoFe2O4 nanocrystals.