Sintering process and grain growth of Mn-Zn ferrite nanoparticles

The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.

Enhancing layered perovskite ferrites with ultra-high-density nanoparticles via cobalt doping for ceramic fuel cell anode

Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration.Herein,we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials.CoFe alloy nanoparticles with ultra-high-density are exsolved on the(PrBa)_(0.95)(Fe_(0.8)Co_(0.1)Nb_(0.1))2O_(5+δ)(PBFCN_(0.1))surface under reducing atmosphere,providing significant amounts of reaction sites and good durability for hydrocarbon catalysis.Under a reducing atmosphere,cobalt facilitates the reduction of iron cations within PBFCN_(0.1),leading to the formation of CoFe alloy nanoparticles.This formation is accompanied by a cation exchange process,wherein,with the increase in temperature,partial cobalt ions are substituted by iron.Meanwhile,Co doping significantly enhance the electrical conductivity due to the stronger covalency of the Cosingle bondO bond compared with Fesingle bondO bond.A single cell with the configuration of PBFCN_(0.1)-Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)|SDC|Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF)-SDC achieves an extremely low polarization resistance of 0.0163Ωcm^(2)and a high peak power density of 740 mW cm^(−2)at 800℃.The cell also shows stable operation for 120 h in H_(2)with a constant current density of 285 mA cm^(−2).Furthermore,employing wet C_(2)H_(6)as fuel,the cell demonstrates remarkable performance,achieving peak power densities of 455 mW cm^(−2)at 800℃and 320 mW cm^(−2)at 750℃,marking improvements of 36%and 70%over the cell with(PrBa)_(0.95)(Fe_(0.9)Nb_(0.1))_(2)O_(5+δ)(PBFN)-SDC at these respective temperatures.This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials,paving the way for the development of high-performance ceramic fuel cell anodes.

Faujasite zeolite decorated with cobalt ferrite nanoparticles for improving removal and reuse in Pb^2+ions adsorption

Water pollution caused by heavy metals ions has been gaining attention in recent years,increasing the interest in the development of methodologies for their efficient removal focusing on the adsorption process for these purposes.The current challenge faced by adsorption processes is the adequate adsorbent immobilization for removal and reuse.Thus,the present work aimed at producing a faujasite zeolite nanocomposite decorated with cobalt ferrite nanoparticles for Pb^2+ions adsorption in an aqueous medium improving magnetic removal and reuse.As a result,a high surface area(434.4 m^2·g^-1)for the nanocomposite and an 18.93 emu·g^-1 saturation magnetization value were obtained,indicating magnetic removal in a promising material for adsorption process.The nanocomposite regeneration capacity evaluated by magnetic recovery after 24 h suspension presented a high Pb^2+ion adsorptive capacity(98.4%)in the first cycle.Around 98%of the Pb^2+ions were adsorbed in the second cycle.In this way,the synthesized faujasite:cobalt ferrite nanocomposite reveals itself as a promising alternative in adsorption processes,aiming at a synergic effect of FAU zeolite high adsorptive activity and the cobalt ferrite nanoparticles magnetic activity,allowing for adsorbent recovery from the aqueous medium via magnetic force and successive adsorptive cycles.

Synthesis and characterization of carbon-coated cobalt ferrite nanoparticles

Cobalt ferrite nanoparticles（CFNPs） were prepared via a reverse micelle method. The CFNPs were subsequently coated with carbon shells by means of thermal chemical vapor deposition（TCVD）. In this process, acetylene gas（C2H2） was used as a carbon source and the coating was carried out for 1, 2, or 3 h at 750℃. The Ar/C2H2 ratio was 10：1. Heating during the TCVD process resulted in a NP core size that approached 30 nm; the thickness of the shell was less than 10 nm. The composition, structure, and morphology of the fabricated composites were characterized using X-ray diffraction, simultaneous thermal analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and selected-area diffraction. A vibrating sample magnetometer was used to survey the samples＇ magnetic properties. The deposited carbon shell substantially affected the growth and magnetic properties of the CFNPs. Micro-Raman spectroscopy was used to study the carbon coating and revealed that the deposited carbon comprised graphite, multiwalled carbon nanotubes, and diamond-like carbon. With an increase in coating time, the intensity ratio between the amorphous and ordered peaks in the Raman spectra decreased, which indicated an increase in crystallite size.

Comparable Studies of Adsorption and Magnetic Properties of Ferrite MnFe_2O_4 Nanoparticles,Porous Bulks and Nanowires

The spinel ferrites MnFe2O4 nanowires were synthesized by hydrothermal route,porous MnFe2O4 and nanoparticles morphologies were synthesized by sol-gel method with egg white.The structures,morphologies,magnetic properties and adsorption properties of these obtained ferrites with different morphologies were studied contrastively.Results show that the obtained samples exhibit ferromagnetic properties.This realizes convenient magnetic separation from solution when they are used in the treatment of organic dyes wastewater.However,the contrastive studies show that the saturation magnetizations（Ms） of MnFe2O4 with different morphologies are different and the Ms follows the order：Ms（porous）〈Ms（nanoparticles）〈Ms（nanowires）.In addition,the adsorptions of methylene blue（MB） onto these ferrites depend on ferrites＇ morphologies seriously.The adsorption rate of MB on the porous MnFe2O4 is much higher than those onto the other two samples because the porous structure can provide high efficient mass transport through the pores.

Radio-frequency-heating capability of silica-coated manganese ferrite nanoparticles

MnFe204 nanoparticles （NPs） with various sizes and tight size-distribution were synthesized by a chemical solution- phase method. The as-synthesized NPs were coated with a silica shell of 4 nm-5 nm in thickness, enabling the water- solubility and biocompatibility of the NPs. The MnFe204 NPs with a size of less than 18 nm exhibit superparamagnetic behavior with high saturated magnetization. The capacity of the heat production was enhanced by increasing particle sizes and radio frequency （RF） field strengths. MnFe204/SiO2 NPs with 18-nm magnetic cores showed the highest heat- generation ability under an RF field. These MnFe204/SiO2 NPs have great potentiality to cancer treatments, controlled drug releases, and remote controls of single cell functions.

Synthesis and Characterization of Ni-Zn Ferrite Nanoparticles (Ni_0.25Zn_0.75Fe₂O₄) by Thermal Treatment Method

Cubic structured nickel-zinc ferrite nanoparticles (Ni0.25Zn0.75Fe2O4) have been synthesized by thermal treatment method. In this procedure, an aqueous solution containing metal nitrates as precursors, polyvinyl pyrrolidone as a capping agent, and deionized water as a solvent were thoroughly stirred, dried at 353 K for 24 h, and crushed into powder before calcination to remove organic matters and crystallize the particles. The structure and particle size were characterized by X-ray powder diffraction and transmission electron microscopy. The average particle size increased from 7 to 25 nm with increase of calcination temperature from 723 to 873 K respectively. The magnetic properties were determined by vibrating sample magnetometer and electron paramagnetic resonance electron paramagnetic resonance at room temperature. By increasing the calcinations temperatures from 723 to 873 K it showed an increase of the magnetization saturation from 11 to 26 emu/g and the g-factor from 2.0670 to 2.1220. The Fourier transform infrared spectroscopy was used to confirm the presence of metal oxide bands at all temperatures and the removal of organic matters at 873 K.

Effect of Aluminium Doping on Structural and Magnetic Properties of Ni-Zn Ferrite Nanoparticles

Aluminium doped Ni-Zn ferrite nanoparticles of general formula of Ni0.5Zn0.5AlxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0) have been synthesized by sol-gel auto combustion method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dis-persive X-ray (EDX), Fourier transform spectroscopy (FTIR) and vibrating sample magneto meter (VSM). XRD studies confirm that all compositions show single phase cubic spinel structure. The crystallite size was calculated using the Debye-Scherrer formula and found in the range of 17 - 52 nm. The lattice parameter “a” is found to decrease with increasing Al3+ content. The SEM images clearly show the crystalline structure and EDX patterns confirm the compositional formation of the synthesized compositions. The results of FTIR analysis indicated that the functional groups of Ni-Zn spinel ferrite were formed during the sol-gel synthesis process. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm-1 and the low frequency band ν2 around 400 cm-1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. As doping is increased the magnetic behavior is found to decrease and the composition x = 2.0 ferrite appears to be exhibiting superparamagnetism as the coercive field and retentivity are found near zero.

Polypyrrole Chitosan Cobalt Ferrite Nanoparticles Composite Layer for Measuring the Low Concentration of Fluorene Using Surface Plasmon Resonance

Fluorene is a polycyclic aromatic hydrocarbon, which is a hazardous toxic chemical in the environment. The measurement of low concentrations of fluorene is a subject of intense interest in chemistry and in the environment. Polypyrrole chitosan cobalt ferrite nanoparticles are prepared using the electrochemical method. The prepared layers are characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The layers are used to detect fluorene using the surface plasmon resonance technique at room temperature. The composite layer is evaluated after detection of fluorene using atomic force microscopy. The fluorene is bound on the layer, and the shift of the resonance angle is about 0.0052°, corresponding to the limitation of 0.01 ppm.

Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe2O4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900℃for 2 h has an average diameter of 60 ~ 90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

Effects of Ce^(3+) doping on the structure and magnetic properties of Mn-Zn ferrite fibers

Ce3+-doped Mn-Zn ferrite fibers were successfully prepared by the organic gel-thermal decomposition method from metal salts and citric acid. The composition,structure,and magnetic properties of these ferrite fibers were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and vibrating sample magnetometer (VSM). The results show that Mn0.2Zn0.8Fe2-xCexO4 (x = 0-0.04) fibers are featured with an average grain size of 11.6-12.7 nm,with diameters ranging between 1.0 to 3.5 μm and a high ...

Effects of Heating Processing on Microstructure and Magnetic Properties of Mn-Zn Ferrites Prepared via Chemical Co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

Preparation and Magnetic Properties of Mn-Zn Ferrites by the Co-precipitation Method

Mn-Zn ferrites （Mn1-xZnxFe2O4） with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio （R） of the mixed solution and NH4HCO3 solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction （XRD） and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3 exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn （x）, but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.

Magnetic properties and microstructures of SnO_2 doped Mn-Zn ferrites

The effects of additive SnO2 (0.4wt.%), with and without SiO2 (0.02wt.%) and/or CaO (0.04wt.%), on the microstructure and magnetic properties of Mn-Zn ferrites were reported. The results reveal that SnO2 on its own increases the initial permeability (μi) slightly, but SnO2 with SiO2 and/or CaO decreases the values of μi. However, ferrites with SnO2 additions have reduced power losses. The separate contributions of hysteresis loss and eddy current loss to the total power loss show that SnO2 (with or without SiO2 and/or CaO) doping increases the hysteresis loss slightly, but SnO2 doping alone reduces the eddy current loss significantly (～14%). The additions of SiO2 or CaO further decrease the eddy current loss, and by interaction of SnO2-CaO-SiO2, the eddy current loss is reduced by more than 20%. These magnetic and microstructural effects were discussed in terms of the additive-impurity interaction, the existence of grain boundary phases, and the effective bulk and grain boundary resistivities of the ferrites.

Effect of V2O5-CaCO3-Nb2O5 Contents on Properties of Low Power Loss Mn-Zn Ferrites

Effect of the content of dopants in the manganese-zinc ferrites on the low power loss is studied by measuring magnetic properties and observing the grain boundary structures. The Mn0.738Zn0.206Fe2.066O4 composition powders were prepared by using conventional ceramic powder processing technique. The microstructure of grain boundary was observed by scanning electron microscope （SEM）. It has been found that power loss is greatly dependent upon the content of the additives.

Magnetic Hysteresis and Complex Initial Permeability of Cr³⁺Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability (μi’ )decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and (μi’ ) of the samples. The (μi’ ) strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

Effect of Nd Doping on Nanosized Mn-Zn Ferrite

Nanosized Mn-Zn ferrite doped with Nd (Mn_ 0.6Zn_ 0.4Nd_xFe_ 2-xO_4) were fabricated by hydrothermal precipitation route and studied by XRD, TEM, DSC and VSM. The effects of Nd doping on manganese zinc ferrites were discussed. The results show that the samples with a small amount of Nd doping are spinel crystal structure and uniformly nanosized particles with little aggregation. DSC analysis of Mn_ 0.6Zn_ 0.4Fe_2O_4 and Mn_ 0.6Zn_ 0.4Nd_ 0.06Fe_ 1.94O_4 samples both present two exothermic peaks ascribed to the redistribution of Mn 2+, Zn 2+ and Fe 3+ ions in the two sub-lattices (tetrahedral (A) and octahedral (B) sites), and the oxidation of Mn 2+-ions at higher temperatures respectively. The saturation magnetization (M_s) for Mn_ 0.6Zn_ 0.4Nd_xFe_ 2-xO_4 ferrites increase with (x) up to 0.06 and decrease for higher concentrations. And supermagnetic behavior was observed at 25 ℃ in the M-H loops of Mn_ 0.6Zn_ 0.4Fe_2O_4 and Mn_ 0.6Zn_ 0.4Nd_ 0.06Fe_ 1.94O_4 samples for their extremely small sizes.

Effect of Sintering Temperature on Microwave Absorbing Behaviour of Mn-Zn Ferrite

The microwave absorbing behaviour of Mn-Zn ferrite sintered at 1100,1200,1300,1400 and 1500℃ has been investigated.The phase constitution of the ferrite was analyzed by X-ray diffraction.The results show that the ferrite sintered at 1 500℃ has better microwave absorbing prop- erty than those prepared at other temperatures,due to the increase of turbulent loss generated by the formation of excessive Fe^(2+) in deoxidizing of Fe_2O_3 at high temperatures.

Influence of Processing Parameters on the Magnetic Properties of Mn-Zn Ferrites

Pure MnO2, ZnO and Fe2O3 were used to prepare a Mn-Zn Ferrite sample of the nominal composition Mn0.64Zn0.29Fe2.07O4. These oxides were mixed firstly for 1hr, and then were milled for 20 and for 40 hrs. The as-mixed and the milled powders were examined by XRD and ME spectroscopy. The investigated samples were further mixed with PVA, granulated, cold pressed and sintered at different temperatures (1000, 1300 and 1400 oC) for 2 hrs and were then reinvestigated again. The magnetic properties of all samples before and after sintering were characterized using VSM at a field of 15 k Oe. When the powder oxides were milled for 20 hrs, detectable diffusion reaction was observed where the centers of all XRD peaks (due to Fe2O3 and MnO2) shifted to higher 2? angles, suggesting that Zn2+ cations had diffused through Fe3+ and/or Mn4+ lattices. The observed increase in the width of the XRD peaks can be attributed to the refinement of the powders by milling. Milling of the powder for 40 hrs resulted in the formation of spinel phase of (Zn, Fe), but MnO2 was disappeared probably due to the formation of amorphous structure. Sintering at 1000, 1300, and 1400 oC resulted in the formation of different spinel (Mn-Zn) ferrites. The ME measurements followed the gradual formation the manganese zinc ferrite until complete formation which observed in the sample that milled for 40 hrs followed by sintering at 1300 oC for two hrs. However, it can be concluded that, the processing conditions of such sample represent are the best conditions for obtaining a soft manganese zinc ferrite (single phase).

The Influence of Zn²⁺Ions Substitution on the Microstructure and Transport Properties of Mn-Zn Nanoferrites

The effect of Zn2+ ions on the microstructure and electrical properties of Mn1-xZnxFe2O4 (0.0 ≤ x ≤ 0.5 in steps of 0.1) through a solid state reaction has been investigated. The structural properties have been investigated using X-ray diffraction (XRD) technique. The XRD analysis confirms that all samples are in a single-phase cubic spinel structure. The experimental lattice parameter (aexp) was decreased with increasing Zn2+ ions substitution due to the smaller ionic radius of zinc content. The crystallite size (t) of samples was estimated by Scherrer’s formula and found in the range (90 - 115 nm). Dc electrical resistivity and Seebeck voltage coefficients were measured as a function of temperature using the two probe methods. The temperature variation of resistivity exhibits two breaks, each break referring to a change in the activation energy. The Curie temperature estimated from dc resistivity measurement decreases with increasing Zn2+ ions. Seebeck voltage coefficient measurements reveal n-type conduction for all samples.