Mn Ferrites Research Articles

Polymetallic red mud direct materialization strategy towards zero waste emission: Electromagnetic wave absorption conversion and sodium solidification

Red mud is an industrial hazardous alkaline solid waste, whereas it is rich in polymetallic components showing a high comprehensive utilization value. Direct materialization of red mud towards zero waste emission is a more reasonable and environmentally friendly strategy. In this work, a novel materialization approach of red mud via converting the polymetallic constituents into functional ferrite material by phase reconstruction with MnO2 was proposed. The mineral phase reconstruction, microstructure evolution, reaction interface observation, electromagnetic property, and the materialization conversion mechanism were investigated. It was found that the complicated phases in red mud were transferred to simple forms including the magnetic ferrites (Ca/Na/Al/Ti-bearing Mn ferrite) and weakly magnetic silicates ((Na,Al,Ca)2SiO3) after phase reconstruction. The reconstructed red mud after sintering at 1200 ℃ for 120min in air atmosphere had satisfactory electromagnetic property. Magnetism study demonstrated the soft magnetic property with maximum saturation magnetization of 34.22emu/g and coercivity of only 7.0Oe. Compared with the original red mud, effective electromagnetic wave absorption with reflection loss (RL) values of the reconstructed red mud below -20 dB were satisfied across a wider frequency bandwidth of 5-18GHz, and the minimum RL value was lower as -32.4dB with a thinner veneer thickness of 15mm, highlighting its excellent electromagnetic wave absorption performance. Moreover, Na solidification behaviors indicated that Na was solidified in the sintered product, which can reduce the possible environmental hazards of red mud alkalinity. The novel materialization treatment with zero waste emission exhibits a favorable application prospect with a large red mud batching ratio about 50wt%.

Hardening mechanism and thermal-solid coupling model of laminar plasma surface hardening of 65 Mn steel

In the present work, the laminar plasma surface hardening method is employed to enhance the service life of metal components fabricated from 65 Mn steel. The mechanical and wear behaviors of the laminar plasma surface hardened 65 Mn steel were analyzed. The martensite transition transformation of the temperature of the laminar plasma-hardened 65 ferrite Mn steel was determined by a thermal-solid coupling model. Based on the orthogonal experimental results, the optimal hardening parameters were confirmed. The scanning velocity, quenching distance and arc current are 130 mm/min, 50 mm and 120 A, respectively. The pearlites and ferrites are transformed into martensites in the hardened zone, while the ratio of martensite in the heat-affected zone decreases with the increase in the hardening depth. Compared to the untreated 65 Mn steel, the average hardness increases from 220 HV0.2 to 920 HV0.2 in the hardened zone and the corresponding absorbed power increases from 118.7 J to 175.5 J. At the same time, the average coefficient of friction (COF) decreases from 0.763 to 0.546, and the wear rate decreases from 5.39×10−6 mm3/(N·m) to 2.95×10−6 mm3/(N·m), indicating that the wear resistance of 65 Mn steel could be significantly improved by using laminar surface hardening. With the same hardening parameters, the depth and width of the hardened zone predicted by the thermal-solid coupling model are 1.85 mm and 11.20 mm, respectively, which are in accordance with the experimental results; depth is 1.83 mm and width is 11.15 mm. In addition, the predicted hardness distributions of the simulation model are in accordance with the experimental results. These results indicate that the simulation model could effectively predict the microstructure characteristics of 65 Mn steel.

Investigation of annealing temperature effect on structural, morphological, optical, magnetic, and dielectric properties of cobalt-doped manganese ferrites

Spinel ferrite Mn0.95Co0.05Fe2O4 was prepared via chemical co-precipitation routes and annealed at four distinct temperatures of 600 °C, 650 °C, 700 °C, and 750 °C. The XRD peak confirmed a single-phase cubic spinel structure, with an increasing crystallite size of 21.64–23.98 nm by the annealing effect. The TEM images show an increase in particle size with rising annealing temperature and indicate well-defined nanocrystalline Mn-Co ferrite. FT-IR spectra detected two vibrational modes at interstitial sub-lattice sites, identifying Co-O, Mn-O, and Fe-O bonds with the spinel structure of Mn-Co ferrite. UV–vis–NIR reflectance revealed an optimal direct band gap of 3.76–4.70 eV, indicating a scope of semiconducting behaviors in the nanocatalysts. In the magnetic hysteresis curve, saturation magnetization decreased while coercivity increased with rising annealing and crystallite size. The M-T loop reveals the Curie temperature of Mn-Co ferrite decreases from 533.84 °C to 382.74 °C. Frequency-dependent complex permeability at different annealing temperatures shows stable initial permeability over a wide frequency range (1 kHz to 100 MHz) and a quality factor several times higher due to reduced magnetic tangent loss. The real dielectric constant and losses decline in rising alternating fields (100 Hz to 1 MHz) and stabilize at higher frequencies following Maxwell-Wagner-type polarization. Eventually, structural, morphological, and magnetic properties are performed relatively well at higher annealing temperatures, and optical and dielectric properties are performed at lower annealing temperatures.

Synthesis, characterization and correlation studies on the Ni–Zn–Mn ferrite as a photocatalyst

Samples of Ni0.3Zn0.7−xMnxFe2O4 (x = 0, 0.15, 0.25, 0.35, 0.45, 0.55) nanoparticles (NPs) were synthesized by auto-combustion flash method. These ferrites were used as catalysts for photodegradation of methylene blue (MB) dye utilizing visible light energy. Structural analysis was carried out using the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, while nanoparticle dimensions were elucidated through transmission electron microscopy (TEM). The magnetic and optical behaviours were unveiled via vibrating sample magnetometer and UV–VIS spectroscopy, respectively. The XRD outcomes established the presence of a cubic spinel-type structure for the studied ferrite samples. The FTIR spectra unveiled two absorption characteristic bands of the spinel ferrite. TEM images revealed nanoscale dimensions of ferrite NPs with the range from 21.1 to 51.8 nm. The optical features exhibited an indirect band gap energy spanning from 4.25 to 4.36 eV. Magnetization behaviour displayed a sinusoidal trend corresponding to varying Mn concentrations. The ferrite NPs catalyst (10 mg) yield photodegradation efficiency ranged from 22.8 to 33.9% for 100 ml MB dye solution after 120 min of light irradiation. The effects of dye concentration and catalyst dose on the degradation efficiency were examined using the Ni0.3Zn0.35Mn0.35Fe2O4 catalyst with highest degradation (= 33.9%). On the other hand, the dependence of the degradation efficiency on the structure, morphological, magnetic and optical properties of the photocatalyst was investigated. The findings of this study underscore the potential of the prepared ferrite nanoparticles for advanced applications in environmental restoration.Graphical abstract

Structural, optical, and dielectric properties of Co0.6Mn0.4GdxFe2-xO4 ferrites prepared through sonochemical method

Gadolinium-substituted cobalt manganese ferrite nanoparticles with the composition Co0.6Mn0.4GdxFe2-xO4 (where x ranges from 0.0 to 0.08, with x = 0.02) were prepared through the sonochemical method. X-ray diffraction reveals that grown samples are single-phase cubic spinel belonging to space group Fd3m, where the crystallite sizes decrease with increasing Gd3+ content. At high doping ratios (x > 0.06), there was a slight increase in crystallite size compared to that of pure Co–Mn ferrite (x = 0), while the lattice parameter (a) decreased in the low doping range of Gd (x < 0.06), resulting in a reduction in crystallite size. Bertaut's method confirms that 80 % of the tetrahedral (A) sites were occupied by Mn ions, while the remaining sites were occupied by other cations in the octahedral (B) positions. Gd3+ ions were found exclusively in the octahedral-B sites. Co2+ ions were expected to occupy the octahedral-B site, which was confirmed in this study for the x = 0.0 and 0.02 samples. Field emission scanning electron microscopy shows the samples are agglomerated and have dense structures. Fourier transform infrared and Raman spectra validated the presence of spinel ferrite modes. Dielectric investigations indicate that as the Gd3+ content exceeds x = 0.0, the dielectric constant and dielectric loss decrease at lower frequencies. The observed dielectric behavior exhibited typical dispersion patterns attributed to Maxwell-Wagner polarization. Furthermore, changes in dielectric properties were observed as the Gd3+ content in Co0.6Mn0.4GdxFe2-xO4 nanoparticles increased, which can be attributed to the presence of oxygen vacancies and variations in the distribution of Fe3+ ions at both A and B-sites.

Multifunctional Nanoparticles with Superparamagnetic Mn(II) Ferrite and Luminescent Gold Nanoclusters for Multimodal Imaging.

Gold nanoclusters (AuNCs) with fluorescence in the Near Infrared (NIR) by both one- and two-photon electronic excitation were incorporated in mesoporous silica nanoparticles (MSNs) using a novel one-pot synthesis procedure where the condensation polymerization of alkoxysilane monomers in the presence of the AuNCs and a surfactant produced hybrid MSNs of 49 nm diameter. This method was further developed to prepare 30 nm diameter nanocomposite particles with simultaneous NIR fluorescence and superparamagnetic properties, with a core composed of superparamagnetic manganese (II) ferrite nanoparticles (MnFe2O4) coated with a thin silica layer, and a shell of mesoporous silica decorated with AuNCs. The nanocomposite particles feature NIR-photoluminescence with 0.6% quantum yield and large Stokes shift (290 nm), and superparamagnetic response at 300 K, with a saturation magnetization of 13.4 emu g-1. The conjugation of NIR photoluminescence and superparamagnetic properties in the biocompatible nanocomposite has high potential for application in multimodal bioimaging.

A DFT study of the structural, magnetic, electronic, mechanical and optical properties of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites: Optoelectronic applications

DFT calculations were used to investigate the structural, magnetic, electronic, mechanical and optical properties of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites by employing the CASTEP Code. The simulated XRD of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites revealed an increase in lattice constants (8.353–8.501 Å), d-spacings (2.426–2.592 Å), the volume of the unit cell (582.811–614.342 Å3), hopping lengths (LA = 7.234–7.441 Å; LB = 5.906–6.074 Å) and a decrease in X-ray density (5.376–5.035 g/cm3). The M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites exhibited the characteristics of direct bandgap semiconductor materials, which increased from 0.931–1.176 eV The computed DOS revealed that M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites exhibited good spin polarization behavior as well, and according to Hirshfeld analyses, the magnetic moment from 3.348–1.436 μB and saturation magnetization from 79.264–34.435 emu/g were increased. The cubic crystal mechanical stability criteria of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites indicated that all ferrites were mechanically stable as potential candidates in electrochemical applications. The values of Pugh's ratio of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites predicted the ductile nature of all ferrites and all the values of Poisson's ratio exhibited the behavior of ionic bonds of all ferrites. The optical characteristics of M0.75Cu0.25Fe2O4 (M = Co, Ni, Mg, Mn) ferrites lie in visible regions, which proved suitable candidates in optoelectronic applications.

Preparation and properties of CaO-added Mn-Zn ferrite ceramic

In the present work, spinel ferrite Mn0.76Zn0.24Fe2O4 were fabricated at the presence of the 0, 0.15, 0.30, 0.45 wt% CaO addition. The synthesis of Mn-Zn ferrites was accomplished using solid-state reaction of oxidative powders. The samples were created by sintering the powdered synthetic spinel. The findings show that any Fe2O3 that persisted after calcination at 1100 °C vanished after further sintering at 1250 °C, and all of the spinel structure-related diffractions in the X-ray diffraction (XRD) patterns were found. The scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analyses indicated the well-dispersed metallic cations in the spinel structure and solution of Ca ions. Theoretical density of sintered sample was improved by CaO addition, and a maximum value 96.2 % of theoretical density was obtained with addition of 0.30 wt% CaO. Increasing CaO content from 0 to 0.30 wt% causes increasing the saturation magnetization (Ms) from 34.6 to 42.4 emu/g in terms of the substitution of Ca2+ cations in the tetrahedral sites. Further increasing of CaO to 0.45 wt% causes decreasing Ms to 33.4 emu/g as a result of octahedral occupation of Ca2+ cations.

Structural and temperature dependent dielectric properties of doped Mn ferrite system

In this work, we have synthesized the Mn1-xAxFe2O4 (A = Zn, Cr; x = 0.5) ferrites. The synthesis of nanoparticles is done with the help of a low temperature gel autocombustion method. Structural confirmation of the nanoparticles is performed by the X-ray diffraction method. A synchrotron X-ray source is also used for structural analysis. Both methods approve the construction of a single phase of Cr doped ferrite, while a small amount of impurity phase of α-Fe2O3 is observed in Zn doped Mn ferrite. With the doping of Cr ions, particle size is enhanced. Dielectric spectroscopy is used to observe the effect of larger Cr ions on the ferrite system. Also, a dielectric study has been performed at high temperatures to see the impact on tangent loss, conductivity, and dielectric behavior. The result shows that the dielectric constant for both samples increases with the rise in temperature. The same behavior is observed in both samples when they are studied with respect to changes in frequency. Zn and Cr doped Mn ferrite samples sintered at 800 °C showed higher ac conductivity with 1.39 × 10−2 S m−1 and 1.0 × 10−2 S m−1 at 300 K and increased to 1.08 × 10−1 S m−1 and 0.1 × 10−1 S m−1 at 573 K when the applied frequency was 10 MHz. The activation energy for the Cr doped sample is marginally higher than the Zn doped sample observed at 1 MHz. This makes the Cr doped Mn ferrite sample a potential candidate for storage device applications as compared to Zn doped Mn ferrites.

Magnetic properties of Mn/Co substituted nano and bulk Ni–Zn ferrites: A comparative study

The present work shows the comparative studies on the magnetic properties of Ni0.4Zn0.6-xCoxFe2O4, (Ni–Zn–Co) and Ni0.4Zn0.6-xMnxFe2O4 (Ni–Zn–Mn) with x = 0.00 to 0.25 in steps of 0.05, ferrites synthesized by sol-gel autocombustion and conventional ceramic methods. Rietveld refinement data confirms the formation of single phase - spinel crystal structure in all the samples. The role of ferromagnetic dopants like Co and Mn on the structural, microstructural, magnetic characteristics such as Curie temperature (Tc), saturation magnetization and coercivity of NiZnFe2O4 ferrite are investigated. The influences of crystallite size obtained by using two different synthesis methods on different magnetic properties are highlighted. Continuous Tc increases have been noticed in both instances along with increasing dopant concentrations. However, compared to Ni–Zn–Mn ferrites, Ni–Zn–Co ferrites display greater Tc values. The experimental observed magnetic moments measured from vibrating sample magnetometer (VSM) are fitted with the theoretical data. The saturation magnetization values exhibit a marginal increase in the bulk form of the material as compared to its nanocrystalline counterparts. On the basis of distribution of cation and exchange interactions between magnetic cations at its tetrahedral and octahedral sublattices, the typical mechanisms accountable for the observed trends were elucidated. In addition, the dc-resistivity and dielectric loss are measured to show the application aspects of the materials in various potential device applications.

Influence of Fe2+ substitution on FTIR and Raman spectra of Mn ferrite nanoparticles

The effect of Fe2+ substitution on FTIR and Raman spectra of Mn ferrites (Mn1−xFexFe2O4; x = 0.0, 0.1, 0.2, 0.4, and 0.6) nanoparticles, synthesized using the co-precipitation method, has been studied. The FTIR spectra of the synthesized nanoparticles have high-frequency bands of ∼ 510–530 cm−1 corresponding to the vibrations of tetrahedral sites (ν1) and low-frequency band (ν2) of ∼ 430–460 cm−1 revealing vibrations of octahedral sites. The shifting of wavenumber with Fe2+ substitution revealed the presence of Fe2+ on the octahedral sites. The Raman peaks were obtained at 191 cm−1, 327 cm−1, 573 cm−1, 605 cm−1, and 674 cm−1 for pure Mn ferrite nanoparticles and shifted with Fe2+ substitution showing the presence of Fe2+ at the octahedral sites.

Corchorus Olitorius-Mediated Green Synthesis and Characterization of Nickel and Manganese Ferrite Nanoparticles

Developing a method for preparing Ni and Mn ferrites was the main objective of this study due to the importance of these materials in high-frequency applications. These ferrites were made by assisting combustion with dried leaves of Corchorus olitorius and then heating them to 700 °C. Several methods, including FTIR, XRD, TEM, and SEM/EDX, were used to characterize these ferrites. The thermal behavior, surface and magnetic properties of the as-prepared materials were determined. The results revealed that the method used is cheap, economical, environmentally friendly and makes it easy to produce the studied ferrites. FTIR, XRD, TEM, and SEM/EDX analyses show the formation of nanocrystalline ferrites with brittle, spongy and spinel-type structures, having two main vibration bands located around 400 cm−1 and 600 cm−1. However, TG-DTG results display the thermal behavior of different materials which consisted of unreacted oxides, carbon and the corresponding ferrites in the range of 300 °C to 600 °C. Moreover, complete conversion of the unreacted oxides to the equivalent ferrite was achieved by increasing heat treatment from 600 °C to 1000 °C. Ferrites are heated at 700 °C, which reduces their surface area. The magnetic properties of different ferrites calcined at 700 °C were estimated using the VSM technique. The magnetism of Fe-based materials containing Ni and Mn is 12.189 emu/g and 25.988 emu/g, respectively. Moreover, the squareness and coercivity of Ni ferrite are greater than for Mn ferrite.

Structural, optical, and electrical properties of Mn0.9La0.1Fe2O4 nanocrystalline ferrites and its synthesis through sol-gel method

This work reports the formation of La-doped nano-crystalline manganese ferrite Mn0.9La0.1Fe2O4 through sol–gel route and examined using XRD and dielectric spectroscopy techniques. The single-phased cubic spinel structure of the ferrite is supported by X-ray diffraction (XRD). The mean crystallite dimension appraised from XRD data has been found to be 21 nm and 11 nm for un-doped and La3+ doped MnFe2O4, respectively, along with a significant rebate in the optical band gap. At room temperature, the frequency-dependent dielectric properties were studied in the frequency range (42 Hz − 5 MHz). The dielectric constant of both the samples narrowly lowers with enhancing frequency and, consequently, shows exemplary dielectric dispersion. The AC-conductivity of the un-doped samples enhances with increasing frequency while it decreases with doping. The dispersion in ac-conductivity (σac) and dielectric properties imply the ordinary dispersion of Maxwell-Wagner type due to the process of hopping of electrons between the Fe2+ and Fe3+ ions and interfacial polarization. The band gap of energy is evaluated with the help of the UV–visible spectra and found to be decreased when La3+ doped with MnFe2O4 ferrite.

Impact of Gd3+ doping on structural, electronic, magnetic, and photocatalytic properties of MnFe2O4 nanoferrites and application in dye-polluted wastewater remediation.

The present work focuses on developing Gd-doped Mn spinel nanoferrites and their potential application in the photodegradation of water pollutants. The impact of Gd3+ ion substitution on structural, electronic, and magnetic characteristics of manganese ferrites has been studied. Nanocrystalline samples of MnGdxFe2-xO4 (x = 0.0 to 0.10, in step size of 0.02) ferrites were prepared via sol-gel self-ignition route. The Rietveld, XPS, HRTEM, and SAED characterization methods confirmed the formation of phase pure ferrite nanoparticles (~ 8-22nm) in the cubic spinel structure. The Gd3+ content in these nanoferrites responded to a systematic reduction in the size of nanocrystallites and an upsurge in the density of nanoferrites. The XPS study revealed fine assimilation of constituent elements in the fcc lattice and ruled out impurities in the nanoferrites. The Fe and the Gd ions were found to be in Fe3+ and Gd3+ states, respectively. While a major fraction of the Mn ions were found to be in the Mn2+ state, a small fraction of Mn4+ ions was observed on the surface of nanoparticles. The nanoferrites were found to exhibit a soft ferromagnetic state from 300 to 20K limits. The highest saturation magnetization was observed for x = 0.02 (MS = 66.6emu/g at 20K). The observed magnetic properties can be understood with the competing (Fe3+ and Mn2+)A-O2--[Fe3+, Mn2+, and Gd3+]B superexchange interactions and magnetocrystalline anisotropy. Due to the small band gap energy of Gd-doped Mn ferrites than that of the pure Mn ferrite, they have demonstrated excellent photocatalytic activity for the degradation of methylene blue (MB) dye under visible light illumination. As much as 96.35% of the MB dye was found to get degraded in 70min of light illumination over synthesized nanoparticles and the photodegradation reaction followed pseudo-first-order kinetics. The increased optical absorbance due to lower band gap, suppressed recombination rate of charge carriers, and enhanced charge mobility make them effective visible light active photocatalysts. This study revealed that the electronic, optical, and magnetic properties of MnFe2O4 nanoferrites could be easily tuned by varying the Gd3+ content and the prepared Gd-doped MnFe2O4 nanomaterials have boundless potential to be utilized in the future making promising active photocatalysts and degradation of harmful industrial dyes for enhanced protection in the fields of environment and health care.

Synthesis, characterization, and magnetic properties of Mn nanoferrites

Nanoparticles of Mn ferrite (MnxFe3−xO4, x = 0.0, 0.2, 0.6, and 0.8) have been successfully prepared by the co-precipitation method using the organic base ethanolamine as the chelating agent. The XRD measurements show well crystalline nano-ferrite particles with a lattice parameter gradually increasing with increasing Mn ions substitution. In contrast, XPS spectra show the existence of Mn3+ and Mn4+ with a crystalline size behavior. Small particle sizes and large specific surface areas in the range of 180–120 m2/g have been detected by HRTEM and BET measurements. The large values of specific surface areas nominate the samples to be good candidates for chemical and biological applications. The FT-IR and Raman spectra have supported the Rietveld refinement of XRD without forming any impurity phases. As Mn doping increases, the FMR and VSM mea-surements have indicated magnetic enhancement in the Mn nanoferrite.

Detailed analysis of lanthanum impact on structural, morphological and magnetic properties of manganese spinel ferrites (MnLaxFe2-xO4 x = (0.0, 0.1, 0.2) synthesized through hydrothermal technique

Hydrothermal method was used for the preparation of lanthanum (La) substituted manganese (Mn) ferrites (MnLaxFe2-xO4, x = 0.0, 0.1, 0.2) to study the effects of La substitution on structural, morphological, and magnetic characteristics. Experimental characterizations such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and Two Probe technique were employed on the prepared samples. A single-phase spinel structure was confirmed by XRD results and lattice parameter increased from 8.40 Å to 8.51 Å with increasing La3+ contents. SEM micrographs showed nanoparticles are agglomerated and non-uniform in size. EDX analysis confirmed that substitution has been successfully achieved. The Raman spectra confirmed that the Raman mode is around 142 cm−1 for pure manganese ferrite and this Raman mode shifted towards lower frequency with increasing the La3+ content. The FTIR spectrum revealed the absorption band of octahedral site is around 650 cm−1 for pure Mn ferrite and this band shifted towards lower frequency with increasing the La3+ content because substitution of La increases the bond length. The M−H loops justified that substitution of nonmagnetic La3+ causes to decrease the saturation magnetization (Ms) as well as coercivity (Hc). The substitution of La3+ increases the resistivity of the Mn ferrite which will make these materials favorable for such applications where low eddy current losses is a primary requirement.

Effect of Mediator on the Auto Combustion Synthesis, Magnetic Properties, and Electron Density Distribution of Spinel Ferrite Mn0.05Zn0.95Fe2O4

Effect of Mediator on the Auto Combustion Synthesis, Magnetic Properties, and Electron Density Distribution of Spinel Ferrite Mn0.05Zn0.95Fe2O4

Structural, magnetic, magnetostrictive and optical properties of Mn and Cu codoped cobalt ferrite

Magnetostrictive materials have been a sought-after multifunctional material due to their propensity to be used in applications such as sensors, actuators, transducers, and other magnetoelectric devices. Cobalt ferrite (CoFe2O4) is one such commonly used magnetostrictive material due to its high magnetostriction and low cost. This work deals with the synthesis of CoFe2O4 (CFO) by substitution of Cu2+ at the tetrahedral site, Mn3+ at the octahedral site, and simultaneous substitution of Cu2+ and Mn3+ at both sites followed by its subsequent characterization. Hydrothermal method was adopted to synthesize the aforementioned samples. The effect of doping was then studied by analyzing their structural, magnetic, morphology, magnetostrictive, and Mössbauer properties. The obtained results reveal that doping of the transition metal ions is crucial in determining the magnetostrictive characteristics of CoFe2O4. Sequential addition of Cu2+, Mn3+ and their simultaneous addition leads to an enhancement in the piezomagnetic coefficient (dλ/dH)max of the CFO system and considerably reduces the magnetic field corresponding to the peak piezomagnetic coefficient.

The recycle of spent Zn–C batteries and the synthesis of magnetic nanocomposite from graphene nanosheets and ferrite and its application for environmental remediation

In this research work, the well-known manganese zinc ferrite Mn0.8Zn0.2Fe2O4 (MZF) magnetic material ferrite was prepared using an eco-friendly method from spent Zn–C batteries (SZCBs) and doped with the high surface area graphene oxide (GO) nanosheets to form MZF/GO magnetic nanocomposite. The prepared MZF/GO magnetic nanocomposite was characterized using DTA-TG, XRD, FT-IR, TEM, and VSM techniques for examining the morphological structure, functional groups, and magnetic properties of the prepared nanocomposite. The characterization results indicated the formation of the Mn0.8Zn0.2Fe2O4 ferrite, and GO, and the homogenous distribution of the ferrite on the GO nanosheets. MZF/GO magnetic nanocomposite was then used as a solid adsorbent for removing Acid Red (AR) dye from water. The results presented the suitability of the pseudo-second-order kinetic model, exothermic, electrostatic, and the physical nature adsorption process, with a removal capacity of 49.9 mg AR dye per g MZF/GO magnetic nanocomposite. The thermodynamics of the adsorption process showed the spontaneity of the process, with a negative entropy change value of −63.7 J/mol.K, negative enthalpy change value of −34.5 kJ/mol, and negative Gibbs free energy change value of −17.5 kJ/mol, indicating that the adsorption of the AR dye by MZF/GO magnetic nanocomposite is enthalpy-driven-process. Moreover, MZF/GO magnetic nanocomposite could be used for the remediation of real environmental water polluted with AR dye, and also could be used for five consecutive cycles with high efficacy for times for the adsorption/removal of AR dye.

Microwave Sol-gel Synthesis of Co, Ni, Cu, Mn Ferrites and the Investigation of Their Activity in the Oxidation Reaction of Carbon Monoxide

Background: The study effect of microwave radiation on the catalytic properties of transition metal ferrites synthesized by ceramic and sol-gel methods in the oxidation reaction of carbon monoxide into dioxide. Objective: This work aims to study the effect of microwave radiation on the production of cobalt, copper, nickel, and manganese ferrites by sol-gel combustion technology using various organic reagents and to study their catalytic activity in the oxidative conversion of carbon monoxide into dioxide. Methods: Microwave treatment was carried out on a setup based on an EM-G5593V microwave oven (Panasonic) with a magnetron power varying from 300 to 800 W with an operating frequency of 2450 MHz. X-ray phase analysis of the products was carried out on a Bruker D 2Phazer automatic diffractometer. The measurement of the specific surface area of the samples was determined by low-temperature nitrogen adsorption by the multipoint BET method on a SORBI-MS instrument (ZAO META, Russia). IR spectra were recorded using FT-IR LUMOS Bruker spectrometers. The micrographs of samples were analyzed on the Sigma VP (Carl Zeiss Jena) equipment. Results: It was determined that the most active catalysts for the oxidation of carbon monoxide to dioxide are ferrites obtained by the sol-gel combustion method using microwave radiation to "ignite" the gel. Conclusion: The use of microwave radiation in the preparation of ferrites by the sol-gel method with combustion can initiate a self-propagating exothermic combustion reaction in the entire volume of the sample in a very short time, measured in seconds. The catalytic activity in the oxidative conversion of carbon monoxide obtained by this method of ferrites is comparable to the activity of ferrites obtained by the sol-gel method with traditional combustion.