Particle Size Of Ferrite Research Articles

Correlation between particle size and magnetic characteristics of Mn-substituted ZnFe2O4 ferrites

We report synthesis of Zn1−xMnxFe2O4 (x = 0.0, 0.1, 0.3, 0.4 & 0.5) ferrites using sol-gel auto-combustion route while citric acid is used as a fuel. The study is aimed to explore the influence of Mn contents on structural parameters, morphological characteristics and magnetic properties of ZnFe2O4 ferrite samples while the impact of average grain dimensions on magnetic properties inferred from multi domain and single domain particle's effect is also analyzed. X-ray diffraction confirmed the configuration of single phase pure crystalline structure with low concentration of Mn while some impurity peaks were found for higher Mn contents. Lattice parameter was found to increase with increasing Mn contents while crystallite size was decreased. Average grain size was decreased from 240 to 150 nm with increasing Mn concentration which directly affected the magnetic properties. A decrease in saturation magnetization (from 52.35 to 45.80 emu/g) and an increase in coercivity (from 44 to 262 Oe) was observed with increasing Mn contents. A decrease in initial permeability and increase in hysteresis loss with increasing Mn contents was also evident. Coercive field and hysteresis losses were increased with decreasing average grain size while initial permeability was found to decrease with decrease in average grain size.

Influence of particle size on the magnetic spectrum of NiCuZn ferrites for electromagnetic shielding applications

The effect of ferrite particle size on the magnetic spectra (1MHz to 1GHz) of NiCuZn polycrystalline ferrites doped with Co2O3 and Bi2O3 were systematically investigated. The experiments indicate that the ferrite particle size tailored by grinding time and corresponding sintering temperatures is crucial to achieving high permeability, high Q-factor and low magnetic loss, at 13.56MHz for electromagnetic shielding applications especially in the near field communication (NFC) field. It is evident that high-performance NiZnCu ferrite materials are strongly tailored by morphology and microstructure. It is conclusive that fine ferrite particles and relatively low sintering temperatures are favorable to lowering magnetic loss and enhancing permeability. This work has built a foundation for improvement of the ferrite slurry used for fabrication of large area tape-casting ferrite sheets.

The role of pH on the particle size and magnetic consequence of cobalt ferrite

Cobalt ferrite (CoFe2O4) nanoparticles with various size distributions were prepared by a chemical co-precipitation method at different pH condition from 8 to 13. The structural characterizations of the prepared samples were carried out using powder X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscope. The XRD results revealed that a single cubic CoFe2O4 phase with the average crystallite sizes of about 5–24nm were formed. Cation distribution occupancy in tetrahedral and octahedral sites were estimated by employing Rietveld refinement technique. The results showed that the whole series of samples contain a partial inverse spinel structure. FTIR measurements between 370 and 4000cm−1 confirmed the intrinsic cation vibrations of spinel structure of the samples. The room temperature magnetic properties of the samples have been examined using vibrating sample magnetometer. It is found that with increasing the pH of reaction, the magnetization and coercive field could be increased. The sample synthesized at pH~8 and 9 showed superparamagnetic behavior and highest coercive field up to 650Oe is attributed to the sample synthesized with pH~13.

Structural and magnetic study of Al3+ doped Ni0.75Zn0.25Fe2−xAlxO4 nanoferrites

Nanostructured Al3+ doped Ni0.75Zn0.25Fe2−xAlxO4 (x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites were synthesized via the wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950°C. With the doping of Al3+, the particle size of Ni0.75Zn0.25Fe2−xAlxO4 first increased to 47nm at x=0.4 and then decreased down to 37nm at x=1. The main two absorption bands in IR spectra were observed around 600cm−1 and 400cm−1 corresponding to stretching vibration of tetrahedral and octahedral group Fe3+–O2−. Saturation magnetization and hyperfine field values decreased linearly with Al3+ due to magnetic dilution and the relative strengths of Fe–O–Me (Me=Fe, Ni, Zn, and Al) superexchanges. The coercive field showed an inverse dependence on ferrite particle size with minimum value of 82Oe for x=0.4. A continuous drop in Curie temperature was observed with the Al3+ substitution. From the Mossbauer spectral analysis and X-ray diffraction analysis, it is deduced that Al3+ for x<0.4 has no obvious preference for either tetrahedral or octahedral site but has a greater preference for the B site for x>0.4. In nutshell the study presents detailed structural and magnetic, and Mossbauer analysis of Ni0.75Zn0.25Fe2−xAlxO4 ferrites.

Synthesis and Magnetic Properties of Aligned Strontium Ferrites

Reducing the particle size of hexagonal ferrites is known to increase their coercivity effectively. However, the size reduction also enhances the agglomeration that deteriorates the magnetic alignment of these particles. In this paper, hexagonal plate shape strontium ferrite particles with an average size of 700 nm using a facile salt-assisted ultrasonic spray pyrolysis method were synthesized to increase the coercivity and prevent the agglomeration during calcinations process. Sodium chloride (NaCl) was used as a salt, and the reacted powders were sintered at 1050 $^{\circ}{\rm C}$ for 2 h under various oxygen flow rates. With increasing the flow rate of oxygen, the specific saturation magnetization of synthesized strontium ferrite particles increased from 62 to 71 emu/g and the coercivity reached 6000 Oe. Strontium ferrite particles aligned under a magnetic field of about 10 kOe showed that the remanence was 91.85%.

Structural, magnetic and electrical properties of the lithium ferrite obtained by ball milling and heat treatment

The physical properties of ferrites are very sensitive to microstructure, which in turn critically depends on the manufacturing process. Lithium ferrite is synthesized by milling process. The powder was annealed at four different temperatures 600, 800, 1,000 and 1,200 °C. The powder annealed at 600 °C has the spinel structure with some of α-Fe2O3, while the powders annealed at ≥800 °C formed in single-phase cubic spinel structure. Particle size of lithium ferrite is in the range of 26–70 nm, and is dependent on the annealing temperature. The saturation magnetization increased from 22 to 85 emu/g and the coercivity decreases from 124 to 4 Oe with increase in the annealing temperature. The dielectric constant (e’), dielectric loss (tan δ) and ac conductivity (σac) were measured at room temperature as a function of frequency. The results of dielectric properties were explained in terms of Koops phenomenological theory.

Austenite Grain Boundary Pinning during Reheating by Mixed AlN and Nb(C,N) Particles

The present study investigates the role of aluminium nitride (AlN) on grain boundary pinning during reheating in presence of niobium carbonitrides (Nb(C,N)) and subsequent evolution of grain size distribution. Three as continuously cast slabs of high strength low alloy steels containing different levels of Nb (between 0.045 – 0.019 wt%) and Al (between 0.057 – 0.02 wt%) have been characterized in terms of phase balance, ferrite grain size distribution and particle size distribution. Precipitate distributions have also been determined following simulated reheating schedules. The prior austenite grain size distributions after reheating have been correlated with precipitate distribution. Quantification of precipitate and prior austenite grain size distributions after reheating unveils the governing mechanisms for precipitate dissolution/ coarsening. It is observed that grain boundary pinning is controlled by AlN at temperatures below 1 125°C, but by Nb(C,N) at higher temperatures.

Sonochemical Synthesis and Characterization of Manganese Ferrite Nanoparticles

This paper reports sonochemical synthesis and characterization of Mn–ferrite nanoparticles using acetates precursors. Mn–ferrite synthesis requires external calcination of oxide precursors formed by sonication. pH does not play a dominant role in the synthesis. Collisions between metal oxide particles induced by shock waves generated by transient cavitation are unable to cross the activation energy barrier for the formation of ferrite. The calcination temperature is a significant parameter that influences the magnetic properties of ferrites. The size, coercivity, and saturation magnetization of ferrite particles increases with the calcination temperature. Ferrites formed at calcination temperatures of 650, 750, and 850 °C show ferromagnetic behavior with easy axis magnetization. Calcination at 950 °C leads to the formation of rods with grain growth that introduces large shape anisotropy. The magnetization curve for rods does not reach saturation, indicating paramagnetic behavior. The cause leading to this...

Effect of barium ferrite particle size on detachment efficiency in magnetophoretic harvesting of oleaginous Chlorella sp.

Microalgal biofuel is garnering many positive and promising reviews as a fuel for the next generation while research effort continues to improve the efficiency of its harvesting for commercial success. In this report, magnetophoretic harvesting of microalgae is conducted through a three-step process, which includes functionalization of magnetic particles by (3-aminopropyl)triethoxysilane (APTES), magnetic separation, and detachment of magnetic particles by increasing pH to higher than the isoelectric point. Detachment process is specifically focused and found that the use of larger magnetic particles is more efficient for detachment of magnetic particles from algae-particle conglomerates. The detaching efficiency improves from 12.5% to 85% when the particle size is increased from 108 nm to 1.17 μm. Smaller magnetic particles provide larger contact area to microalgae and form strong electrostatic binding to negatively-charged microalgae when pH is lower than the isoelectric point.

Superparamagnetic Behavior of MFe2O4 Nanoparticles and MFe2O4/SiO2 Composites (M: Co, Ni).

Two kinds of nanosized ferrite systems have been prepared: MFe2O4 nanoparticles and MFe2O4/SiO2 (M: Co, Ni) nanocomposites with different ferrite particle sizes. Magnetic measurements have been done for both ferrite systems in the 5–700 K temperature range, and the silica matrix effect on the magnetic behavior has been studied. Whereas CoFe2O4 samples are characterized by high anisotropy values, NiFe2O4 particles seem to be magnetically soft, which may favor the dipolar interactions. The silica matrix avoids all kinds of particle interactions that modify the magnetic behavior. Therefore, in 2–5 nm embedded Co-ferrite particles, a decreasing HC value with the increasing particle size is not observed. This almost constant HC value indicates that interactions between surface spins of different particles are absent for this particle size range. In the case of Ni-ferrite particles, the dipolar interactions between bulk particle moments are minimized due to the presence of the SiO2 matrix.

Size dependent ferromagnetic resonance and magnetic anisotropy of hexagonal barium and strontium ferrite powders

Ferrite powders with different particle diameters were characterized in millimeter wave frequency range. Quasi-optical spectrometer in transmission mode powered by high power backward wave oscillator was employed to measure the transmittance of the powder samples. Strong ferromagnetic absorptions were acquired in the millimeter wave frequency range. The absorption frequencies exhibit distinct shift related to the size of ferrite particles. The complex dielectric permittivity and magnetic permeability are determined from the transmittance spectra. The size dependence of ferromagnetic resonance is clearly observed.

Structural and Magnetic study of Al3+ doped Ni0.75Zn0.25Fe2-xAlxO4 nanoferrites

AbstractNanostructured Al3+ doped Ni0.75Zn0.25Fe2-xAlxO4 (x = 0.0,0.2,0.4,0.6,0.8, and 1.0) ferrites were synthesized via wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 °C .With the doping of Al3+, the particle size of Ni0.75Zn0.25Fe2-xAlxO4 first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. Saturation magnetization decreased linearly with Al3+ due to magnetic dilution. The coercive field showed an inverse dependence on the particle size of ferrites.

Synthesis of nonstoichiometric zinc ferrite nanoparticles with extraordinary room temperature magnetism and their diverse applications

A series of nonstoichiometric zinc ferrite (ZndFe3−dO4) nanoparticles with Zn-dopant concentration d ranging from 0 to 0.5 was synthesized via thermal decomposition route employing oleic acid as surfactant. The zinc dopant concentration was controlled by the ratio of Zn/Fe precursors. High room temperature saturation magnetization of 110 emu g−1 was obtained for large Zn ferrite particles (more than 100 nm) with nominal composition of Zn0.468Fe2.532O4. The origin of the extraordinary magnetic property was revealed as the Zn substitution of Fe atoms at the tetrahedral site (A site) in the spinel magnetite phase. It was found that the precursor/surfactant ratio was an important parameter for the control of the shape and size of as-synthesized Zn ferrite particles. The details were investigated through a series of experimental work. Size-dependent applications, such as radar absorption and magnetic fluid hyperthermia, were further studied. Both applications required magnetic particles with high saturation magnetization, hence our samples displayed advantages over Fe3O4 magnetite nanoparticles. Especially for magnetic fluid hyperthermia, 26 nm Zn ferrite nanoparticles coated by P-mPEG polymer showed superior biocompatibility and heating efficiency, implying the potential usefulness to in vivo cancer therapy.

Wear Performance of Cu-Alloyed Austempered Ductile Iron

An investigation was carried out to examine the influence of structural and mechanical properties on wear behavior of austempered ductile iron (ADI). Ductile iron (DI) samples were austenitized at 900 °C for 60 min and subsequently austempered for 60 min at three temperatures: 270, 330, and 380 °C. Microstructures of the as-cast DI and ADIs were characterized using optical and scanning microscopy, respectively. The structural parameters, volume fraction of austenite, carbon content of austenite, and ferrite particle size were determined using x-ray diffraction technique. Mechanical properties including Vicker’s hardness, 0.2% proof strength, ultimate tensile strength, ductility, and strain hardening coefficient were determined. Wear tests were carried out under dry sliding conditions using pin-on-disk machine with a linear speed of 2.4 m/s. Normal load and sliding distance were 45 N and 1.7 × 104 m, respectively. ADI developed at higher austempering temperature has large amounts of austenite, which contribute toward improvement in the wear resistance through stress-induced martensitic transformation, and strain hardening of austenite. Wear rate was found to depend on 0.2% proof strength, ductility, austenite content, and its carbon content. Study of worn surfaces and nature of wear debris revealed that the fine ausferrite structure in ADIs undergoes oxidational wear, but the coarse ausferrite structure undergoes adhesion, delamination, and mild abrasion too.

Magnetism and thermal induced characteristics of Fe2O3 content bioceramics

Magnetic properties of Li2O–MnO2–CaO–P2O5–SiO2 (LMCPS) glasses doped with various amounts of Fe2O3 were investigated. There is a dramatic change in the magnetic property of pristine LMCPS after the addition of Fe2O3 and crystallized at 850°C for 4h. Both the electron paramagnetic resonance and magnetic susceptibility measurements showed that the glass ceramic with 4at% Fe2O3 exhibited the coexistence of superparamagnetism and ferromagnetism at room temperature. When the Fe2O3 content was higher than 8at%, the LMCPS glasses showed ferromagnetism behavior. The complex magnetic behavior is due to the distribution of (Li, Mn)ferrite particle sizes driven by the Fe2O3 content. The thermal induced hysteresis loss of the crystallized LMCPS glass ceramics was characterized under an alternating magnetic field. The energy dissipations of the crystallized LMCPS glass ceramics were determined by the concentration and Mn/Fe ratios of Li(Mn, Fe)ferrite phase formed in the glass ceramics.

Microstructure and mechanical property of cold rolled low carbon steel after prolonged annealing treatment

The effects of ferrite–pearlite and ferrite–martensite starting microstructures on ferrite grain sizes and carbide particle sizes after cold rolling and prolonged annealing treatment have been investigated. Ferrite–martensite starting microstructures showed finer grain and particle sizes and improved tensile properties after cold rolling annealing cycle compared to ferrite–pearlite starting microstructures. A ‘fibrous’ martensite morphology developed by intermediate quenching treatment is more beneficial in that respect compared to the ‘blocky’ martensite morphology obtained from the step quenching treatment.

Sol-gel synthesis of nanostructured perovskite-like gadolinium ferrites

Nanodispersed layered perovskite-like ferrites GdSrFeO4 and Gd2SrFe2O7 have been synthesized for the first time in accordance with the sol-gel technology using the citrate-nitrate technique. The citratenitrate and glycine-nitrate techniques of the synthesis of a complex oxide GdFeO3 with a three-dimensional perovskite structure have been optimized. The decrease of the ferrite particle size from 10 μm in the case of the solid-phase high-temperature synthesis to 50–200 nm in the case of the sol-gel technology has been demonstrated.

Effect of sintering temperature and the particle size on the structural and magnetic properties of nanocrystalline Li0.5Fe2.5O4

Sintering temperature and particle size dependent structural and magnetic properties of lithium ferrite (Li0.5Fe2.5O4) were synthesized and sintered at four different temperatures ranging from 875 to 1475K in the step of 200K. The sample sintered at 875K was also treated for four different sintering times ranging from 4 to 16h. Samples sintered at 1475K have the cubic spinel structure with a small amount of α-Fe2O3 (hematite) and γ-Fe2O3 (maghemite). The samples sintered at≤1275K do not show hematite and maghemite phases and the crystals form the single phase spinel structure with the cation ordering on octahedral sites. Particle size of lithium ferrite is in the range of 13–45nm, and is depend on the sintering temperature and sintering time. The saturation magnetization increased from 45 to 76emu/g and coercivity decreases from 151 to 139Oe with an increase in particle size. Magnetization temperature curve recorded in ZFC and FC modes in an external magnetic field of 100Oe. Typical blocking effects are observed below about 244K. The dielectric constant increases with an increase in sintering temperature and particle size.

Effects of La–Zn substitution on microstructure and magnetic properties of strontium ferrite nanofibers

Sr1−xLaxZnxFe12−xO19/poly(vinylpyrrolidone) (PVP) (0.0≤x≤0.5) precursor nanofibers were prepared by the sol–gel assisted electrospinning method from starting reagents of metal salts and PVP. Subsequently, the Sr1−xLaxZnxFe12−xO19 nanofibers with diameters of around 100 nm were obtained by calcination of the precursor at 800 to 1000°C for 2 h. The precursor and resultant Sr1−xLaxZnxFe12−xO19 nanofibers were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer and vibrating sample magnetometer. The grain sizes of Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers are in a nanoscale from 40 to 48 nm corresponding to the calcination temperature from 800 to 1000°C. With La–Zn substitution content increase from 0 to 0.5, the grain size and lattice constants for the Sr1−xLaxZnxFe12−xO19 nanofibers obtained at 900°C show a steady reduction trend. With variations of the ferrite particle size arising from the La–Zn substitution, the nanofiber morphology changes from the necklace-like structure linking by single elongated plate-like particles to the structure building of multi-particles on the nanofiber cross-section. The specific saturation magnetization of Sr1−xLaxZnxFe12−xO19 nanofibers initially increases with the La–Zn content, reaching a maximum value 72 A m2 kg−1 at x=0.2, and then decreases with a further La–Zn content increase up to x=0.5, while the coercivity exhibits a continuous reduction from 413 (x=0) to 219 kA m−1 (x=0.5). The mechanism for the La–Zn substitution and the nanofiber magnetic property are analyzed.

X-ray Absorption Spectroscopy and Mössbauer Spectroscopy Studies of Superparamagnetic ZnFe2O4 Nanoparticles

Zn ferrite nanoparticles ranging from 3 to 19 nm have been obtained under solvothermal conditions. In addition, two samples of ZnFe2O4/SiO2 nanocomposite of 11 and 20 nm ferrite particle size have ...