Ferrite Parts Research Articles

Study on liquid-phase sintering and magnetic properties of SLA-printed Mn-Zn ferrite ceramics

To obtain Mn-Zn ferrite magnetic ceramic parts with good densification and magnetic properties, a study was conducted. Mn-Zn ferrite magnetic ceramic parts with a solid particle content of 58 vol% were prepared using stereolithography (SLA). The SLA-cured ceramic blanks were degreased and sintered. The degreasing process for Mn-Zn ferrite parts was optimized using a direct heat degreasing method, resulting in a suitable process for the ferrite magnetic ceramic paste system. The method of liquid phase sintering is proposed for sintering the degreased ferrite parts. The study investigated the impact of the content of accelerant, sintering temperature, and holding time on the density and magnetic properties of Mn-Zn ferrite parts. The optimal parameters were found to be a firing aid content of 3 wt%, a sintering temperature of 900 °C, and a holding time of 90 min. Under these conditions, the parts exhibited a density of 4.43 g/cm3, densification of 91.4 %, saturation magnetization strength of 64 emu/g, and coercivity of 10 Oe. Finally, the sintering control mechanism of SLA-printed ferrite magnetic ceramics was analyzed. The study revealed the grain growth process and magnetization principle of Mn-Zn ferrite during liquid phase sintering. This research provides guidance for the subsequent photocuring printing and degreasing sintering of Mn-Zn ferrite ceramics. Additionally, Mn-Zn ferrite magnetic ceramic parts prepared by the SLA method also hold a wide application prospect in various precision electronic components.

Cobalt Ferrite Incorporated Ocimum sanctum Nanocomposite Matrix as an Interface for Adsorption of Organic Dyes: A Sustainable Alternative

AbstractThe preparation of Cobalt ferrite‐Ocimum sanctum nanocomposite, referred to as CoFe2O4/OS, has been reported along with its application for the treatment of water containing hazardous organic contaminants. A simple co‐precipitation approach was applied for synthesis of magnetic nanocomposite, and a thorough analysis for its characterization was conducted using several spectroscopic and microscopic techniques. The characterization results showed that the magnetic nanocomposite exhibited substantial functional groups of Ocimum sanctum powder and magnetic ferrite part. The adsorption investigation of nanocomposite for removal of two cationic dyes was carried out with varying parameters, such as pH, contact time, temperature, concentration, and composite dosage. The sorption process was proved feasible and exothermic at the tested temperatures (303–323 K). The sorption data followed Freundlich and Temkin isotherms which recommended the physisorption progression. The kinetic study revealed a pseudo‐second order rate of sorption process for both dye molecules. The facile preparation, economical cost, significant magnetic character, and high sorption capacity will surely construct the water treatment system more competent with the use of CoFe2O4/OS.

Влияние остаточных напряжений в стали У8 с грубопластинчатым перлитом на магнитную проницаемость

The physical reasons for the formation of peaks of that part of the magnetic permeability, which is caused by transitions of only 90-degree domain boundaries µ90(H0) in deformed steel U8 with coarse-plate perlite when the field changes along the back of the hysteresis loop, are considered. It is shown that the orientation relations of the Patch-Pitch between single-crystal ferrite and cementite plates in U8 steel lead to the appearance of a constant angle between the magnetic moments of these plates and, consequently, to the appearance of corresponding local scattering fields. The latter can significantly affect the values of the peak fields of the curve µ90(H0). Theoretical expressions for these fields containing contributions of scattering fields that should be taken into account when determining residual compressive stresses are obtained. It is also shown that to determine the residual stresses, two expressions for peak fields are not enough, and additional experiments are needed, as which it is proposed to use the dependences of the coercive force on elastic tensile stresses. This leads to a complication of the algorithm for determining residual compressive stresses in comparison with the case of low-carbon steels. A method for estimating the values of local scattering fields in the ferrite parts of U8 steel grains with residual compressive stresses is proposed.

Estimation of residual compressive stresses in deformed U8 steels with coarse-plate perlite by field dependences of magnetic permeability

The physical reasons for the formation of peaks of that part of the magnetic permeability, which is caused by transitions of only 90-degree domain boundaries μ90(H0) in deformed steel U8 with coarse-plate perlite when the field changes along the back of the hysteresis loop, are considered. It is shown that the orientation relations of the Patch-Pitch between single-crystal ferrite and cementite plates in U8 steel lead to the appearance of a constant angle between the magnetic moments of these plates and, consequently, to the appearance of corresponding local scattering fields. The latter can significantly affect the values of the peak fields of the curve μ90(H0). Theoretical expressions for these fields containing contributions of scattering fields that should be taken into account when determining residual compressive stresses are obtained. It is also shown that to determine the residual stresses, two expressions for peak fields are not enough, and additional experiments are needed, as which it is proposed to use the dependences of the coercive force on elastic tensile stresses. This leads to a complication of the algorithm for determining residual compressive stresses in comparison with the case of low-carbon steels. A method for estimating the values of local scattering fields in the ferrite parts of U8 steel grains with residual compressive stresses is proposed. Keywords: residual compressive stresses, deformed steel U8 with coarse-plate perlite, magnetic field, magnetization, magnetic permeability, 90-degree domain boundaries (DB), large-angle vicinity(LAV) and small-angle (SAV) grain boundaries of steel, orientation relations of the Patch-Pitch.

Direct ink writing of dense strontium ferrite parts by staggered and overlapped stacking method

An innovative process was proposed to solve the limitations of direct ink writing (DIW) in the manufacture of dense ceramics. Dense strontium ferrite parts were successfully prepared by DIW. This innovative process that the staggered and overlapped stacking effectively eliminated the gaps among adjacent printing filaments, which could also be applied to other additive manufacturing technologies. The density and mechanical properties of samples were remarkably improved based on theoretical calculation and program setting. Results show that compared with staggered stacking method, the relative density of samples prepared by staggered and overlapped stacking method increased from 97.42 ± 0.20% to 99.35 ± 0.20%, and the surface roughness reduced from 11.42 ± 0.50 μm to 5.48 ± 0.50 μm. The three-point bending strength and compressive strength of sintered samples were 84.00 ± 5.00 MPa and 610.00 ± 20.00 MPa, respectively.

Theoretical Study of the Impedance Matching of the Ferrite Tuner System for ICRF Heating

A theoretical study on a ferrite stub tuner antenna system for ion cyclotron resonance frequency (ICRF) heating is discussed in this paper. High amounts of radio frequency power can be reflected at the antenna as a result of impedance mismatches arising from large changes in the plasma resistance during L- to H-mode transitions or edge localized modes. A fast-response ferrite stub tuner network has been proposed to mitigate these reflections by rapidly varying the impedance to match the rapid load changes on the ICRF antenna. This study numerically shows the influence relationship of the normalized mechanical length and the ratio of the ferrite part of two ferrite stubs on the regulating range of a biasing magnetic field of two stubs. A prematching stub can be used to reduce the standing-wave voltage on the ferrite tuners. The analysis of the ideal position and length of the prestub as well as the distance between the ferrite network and prestub are presented. Numerical simulations demonstrate that selecting ideal values for mechanical length and the ratio of the ferrite part of two ferrite stubs plays an important role in the impedance matching performance of the triple ferrite system during a large variation in plasma resistance.

Effects of groove configuration and buttering layer on the through-thickness residual stress distribution in dissimilar welds

Dissimilar metal welds (DMW) of ferritic to austenitic stainless steel are broadly used in steam generators working in power generation industries. Frequent failure of DMWs from the heat-affected zone (HAZ) of the ferritic part necessitates structural integrity assessment of the DMWs in order to determine and extend the lifetime of these components. In this regard, typical DMWs of SA516–309L–304L and SA516–309L/308L–304L attributed to domestic reactors were fabricated under different welding conditions. The effects of conventional and narrow weld groove configurations, buttering layer, and varying buttering layer width on the through-thickness residual stress fields in the DMWs were investigated experimentally and with the help of numerical simulations. Results show that the narrow groove weld is beneficial in reducing the residual stresses in the weld zone. Incorporating an additional buttering layer in the narrow groove joint further reduced the residual stresses across the weld joint. A 6 mm thick buttering layer was found to be competent enough to minimize the residual stresses dispersed across the weld cross-section.

Magnetic complex permeability (imaginary part) dependence on the microstructure of a Cu-doped Ni–Zn-polycrystalline sintered ferrite

In this study, the effective complex magnetic permeability-imaginary part (μeff'') of a Cu doped-NiZn polycrystalline ferrite used as EMI suppressor has been quantitatively related to microstructural parameters. It has been observed that μeff'' strongly depends on average grain size (G) of the compact, but also on its relative density ϕ: the higher grain size and density the higher μeff''. A mathematical relationship between μeff'' and average grain size and densification has been proposed and tested, accurately reproducing the experimental results. The use of densification concept allows to compare the wide range of microstructures tested and includes a lower value of relative density (estimated around 0,56) below which μeff'' is virtually zero. The grain boundary thickness (δ) has been estimated around 2 nm which is in agreement with experimental results reported in this work and with those found in literature.

Синтез, структура и свойства Zn0,3Ni0,7–xCoxFe2O4 (x = 0–0,6) феррита

For many years, Ni-Zn ferrites with the spinel structure have actively been used as various components for RF devices. An analysis of modern scientific literature has been carried out, as a result of which an alloying element has been determined that will change the complex of physicochemical properties of the initial matrix of Ni-Zn ferrite. The article presents the results of a study of the Zn0.3Ni0.7–xCoxFe2O4 ferrite, where x takes the value 0–0.6 in increments of 0.2. In addition to the alloying element, the properties of the samples under study are affected by selection of the method of obtaining the material, as well as the temperature-time mode of synthesis. The samples have been obtained by the solid-phase synthesis in a tube furnace with silicon carbide heaters at a temperature of 1150 °C for 5 hours of isothermal exposure. The objective of the present study is to obtain new compositions of nickel-zinc ferrite doped by cobalt according to the already known technology for a wider concentration range, as well as investigate their properties. The chemical composition has been analyzed on a Jeol JSM 7001F scanning electron microscope equipped with an Oxford INCA X-max 80 X-ray dispersion spectrometer to determine the actual gross formula of sintered samples, the results of which are in good agreement with the theoretical given formulas. As a result of X-ray phase analysis (RigakuUltima IV), it has been found that all the samples under study are monophasic and have the spinel structure with an Fd-3m space group. Unit cell parameters monotonically increase with increasing cobalt concentration x (Co) (from 8.3643 (4) Å to 8.3983 (4) Å). As a result of the study of DSC curves (Netzsch, STA 449 F1 Jupiter), it has been found that partial replacement of Ni and Zn ions by cobalt ions leads to a decrease in the Curie temperature (from 341 °C to 419 °C). Since ferrite parts are used at various temperature conditions, such alloying makes it possible to effectively control the range of working temperatures of the material.

Interplay between the ferrimagnetic and ferroelectric phases on the large magnetoelectric coupling of xLi0.1Ni0.2Mn0.6Fe2.1O4–(1 − x)Bi0.8Dy0.2FeO3 composites

The multiferroic composites of ferromagnetic Li0.1Ni0.2Mn0.6Fe2.1O4 (LNMFO) and ferroelectric Bi0.8Dy0.2FeO3 (BDFO) with the general formula xLi0.1Ni0.2Mn0.6Fe2.1O4–(1 − x) Bi0.8Dy0.2FeO3 have been prepared by the solid-state reaction route. The XRD analysis has ensured that the composites are composed of a mixture of cubic spinel LNMFO and orthorhombic perovskite BDFO phases. Field Emission Scanning Electron Microscope is used to investigate the surface morphology of the studied compositions. The average grain size of the composites has reduced slightly with the enhancement of ferrite part up to 20% and after that it has increased again. The real part of the initial permeability $$(\mu^{\prime}_{i} )$$ was found to be increasing with ferrite content. The real part of dielectric constant $$(\varepsilon^{\prime})$$ exhibits dispersion at low-frequency region because of Maxwell–Wagner type interfacial polarization. The complex impedance spectroscopy has been used to separate the grain and grain boundary contribution to the total resistance. Existence of the hopping conduction mechanism has been confirmed through the study of electric modulus. The hysteresis loops of the compositions are studied to confirm the response of ferrite part to the applied magnetic field. The magnetoelectric voltage coefficients of the composites have reduced with the ferrite part. The maximum magnetoelectric voltage coefficient is nearly 158 × 103 Vm−1 T−1 for the 0.1LNMFO–0.9BDFO composite, which is about three times of the reported value compared to other composites.

3D gel-printing of Sr ferrite parts

3D gel-printing (3DGP) opens new possibilities to process complex-shaped Sr ferrite parts for magnetic applications. In this study, a novel 3DGP process based on the hydroxyethyl methacrylate gelation system was employed to prepare complex-shaped Sr ferrite samples. To obtain highly loaded pseudo-plastic slurries, the Sr ferrite powder was modified by 1 wt% silane coupling agent and 2.5 vol% polymer Silok7050S was introduced into the ceramic slurry as a dispersant. In the printed samples, good dimensional accuracy and surface quality were achieved with a relatively low surface roughness of 5 µm. After sintering, the Sr ferrite ceramics exhibited good surface quality and the surface roughness was 3.2 µm. A homogeneous microstructure was observed. The bending strength for the sintered samples with the relative density of 97% was 83 MPa. In addition, the corresponding coercivity, remanence, and maximum magnetic energy product values were 271.2 kA/m, 0.383 T, and 26.34 kJ/m3, respectively.

Widening of Laths in Bainite

Units of bainite in Fe-C alloys from the upper temperature range inherit their shape from Widmanstätten plates of ferrite, which are lathlike. The thickness increases by long-range diffusion of carbon and the length by short-range diffusion of carbon from the advancing edge of the tip. Both have been studied extensively and are fairly well understood. Widening growth seems to have been much neglected, but a study of some aspects of widening is now presented. The present report is the last one in a series of four morphological studies of bainite, isothermally formed in Fe-C alloys with 0.3 or 0.7 mass pct carbon, mainly in the upper temperature range. It contains a number of morphological observations made on cross sections of packets of bainite, and it elucidated a number of interesting questions about bainite and resulted in some proposals. The ferrite plates in a packet are nucleated as a group on a grain boundary, not each one separately on the side of a prior plate. Lengthening occurs by advancement of a short edge that is formed in close contact to the grain boundary. Widening of laths does not start spontaneously. It is initiated by a modification of the structure of the long edge of the lath. When it then moves, the lattice of the new ferrite is rotated relative to the ferrite formed by lengthening and the habit plane is different. In a section through the length direction, it is difficult to recognize what part of ferrite has formed by widening growth. Furthermore, it is proposed that the individual plates in a microstructure, previously used to illustrate subunits formed by repeated nucleation, were nucleated on a hidden grain boundary.

Design and research of magnetic tunable frequency selective surface based on dielectric and ferrite

In this paper, a method of designing tunable bandpass frequency selective surface via ceramics and ferrite material is proposed. The ferromagnetic resonance frequency can be tuned when magnetic field is applied. According to this property, the center-frequencies of the pass and stop band can be adjusted. The proposed model is composed of the ceramic part and ferrite part, and CST simulation under C band waveguide condition is employed in the research. For the ceramic part, five high-permittivity rectangular blocks are included. The aim is to achieve negative permittivity in broad band. The band-pass and band-stop properties of the frequency selective surface are clarfied based on the effective medium theory. The stop band originates from a similar Drude resonant electric monopole in the medium. The part of ferrite is composed of ten rectangular blocks. By adjusting the applied magnetic field, the ferromagnetic resonance and negative permeability are obtained at corresponding frequencies. Based on the double negative characteristics, the two parts are combined together to realize the pass band. For instance, when the magnetic field H0 is 1700 Oe, the ferromagnetic resonance appears at a frequency of 6.778 GHz. In this case, the center frequency of the pass band is at 6.758 GHz. By interacting with the electromagnetic wave, the electric resonance can take place in the ceramic blocks, and the ferromagnetic precession will appear in the ferrite blocks. The simulation results indicate that the pass band is switchable and tunable in a range of 6-8 GHz by changing the bias magnetic field. The distributions of electric and magnetic fields, and the parameters of perimittivity, permeability and impedance are obtained and discussed. Finally, the samples are fabricated and tested. The experimental results are basically consistent with the simulation results, indicating that the double negative passband can be adjusted via the applied magnetic field. This proposal provides a route to designing all-dielectric frequency selective surface and it can be used to design multi-band or tunable frequency selective surface.

Superstrate-Based Beam Scanning of a Fabry–Perot Cavity Antenna

Incorporating phased array technique to scan the main beam of a Fabry-Perot cavity (FPC) antenna produces sidelobes proportional to the scan angle. An alternative dielectric-ferrite superstrate-based scan mechanism with controlled sidelobe level is presented in this letter. A beam scan of 24 ° is demonstrated by axially magnetizing the ferrite part of the superstrate with ΔH = 0.25 T. Stepped dielectric part of the superstrate is optimized to reduce the sidelobe level of the FPC antenna by 4.49 dB. The fabricated antenna is tested to verify the simulated radiation patterns and reflection responses. The requirement of magnetic biasing can be considerably reduced using LTCC technology, where biasing coils are embedded within the ferrite superstrate.

Application of copper nanoparticles as additions to a grinding fluid to increase the quality of grinding of magnetic ceramic materials

The influence of copper nanoparticles in a grinding fluid (GF) used for grinding on the characteristics of the surface layer of ferrite parts and their service properties is studied. Profilograms of the ground surfaces and their roughness are measured. The electromagnetic losses of 10000NN ferrite parts ground in an GF medium with copper nanoparticles are estimated. The use of metal nanoparticles as additions to a grinding fluid is shown to be useful for processing of brittle nonmetallic materials.

Brittle fracture analysis of Dissimilar Metal Welds

This paper deals with a fracture mechanics analysis of a narrow-gap Dissimilar Metal Weld (DMW) in the brittle fracture domain. The considered case is a Ni base alloy weld joint between a ferritic component and an austenitic pipe and the aim of the present study is to show that in the same loading conditions, the weld joint is less sensitive to the brittle fracture than the nearby ferritic part of the component.The bases of the proposed qualitative study rely on a stress-based criterion model, using a threshold stress (σth) below which the cleavage cannot occur. From that criterion, brittle fracture risk is evaluated, then compared between two positions of a postulated crack: one in the Heat Affected Zone (HAZ) of the ferritic material, the other in Base Metal (BM) far from the weld joint.For the experimental part of this comparison, one mock-up containing a DMW is used. From this mock-up, a large number of specimens of various types and with various crack locations was tested at low temperature. In parallel to that extensive experimental program, Finite Element Analysis has been done. The main result of that F.E.A. is that, due to the mismatch between the different materials, the brittle fracture risk is lower in the HAZ because of the stress relaxation with plasticity in the weld material and loss of constraint in the cracked section.This paper presents firstly a survey of DMW integrity evaluation, then the criterion used for the comparison, the experimental work and the F.E.A. made to show qualitatively the highest risk of brittle fracture of the homogeneous ferritic material compared to the DMW one.

Computational approach using Johnson–Cook model on dual phase steel

In this research, two different hypo-eutectoid steels with different carbon content and alloying elements were made into samples with dual phase ferrite martensite microstructure. Their morphology and the mechanical properties were then compared. Computational model varying the ferrite percentage was also proposed. The model adopts the failure rule of Johnson–Cook’s. The result shows that the difference in mechanical property was not only due to the variation of the ferrite parts in them but also due to the shapes of the constituents. It tends to follow the continuum mechanics rule. It is also concluded that modeling using two-dimensional approach is sufficient to estimate the properties of the dual phase structure.

Fatigue propagation of long cracks in ferritic thin wall ductile iron castings

The present work focuses on the fatigue propagation of long cracks in ferritic ductile iron parts of varied thickness. Samples were taken from thin wall ductile iron plates and standard 'Y' blocks with nodule counts ranging from 250 to 2200 nod/mm2 and ferrite grain sizes from 70 to 150 μm. Fatigue crack propagation threshold ΔKth and Paris law constants C and m were measured, and the influence of the microstructure refinement (established through nodule count and grain size) on the characteristics of the fatigue fracture surface was analysed. The results show that, once the crack is initiated, the fatigue crack growth threshold diminishes as the microstructure is refined, while the rate of growth remains practically unaltered. The crack path preferentially intersects graphite nodules and is mostly transgranular through the ferrite grains. Nevertheless, at low levels of ΔK, a low percentage of intergranular fracture was also observed.

Influence of zinc substitution on magnetic and electrical properties of MgCuZn ferrite nanocrystalline powders prepared by sol–gel, auto-combustion method

The ferrite compositions Mg 0.80− x Cu 0.20Zn x Fe 2O 4 with x = 0.5, 0.55, 0.60 and 0.63, were synthesized through nitrate–citrate gels auto-combustion method. The autocatalytic nature of the combustion process has been studied by thermal analysis (DTA and TG) of the dried gels. The as-burnt powders were calcined at 800 °C for 1 h and then pressed ferrite parts were sintered at 900 °C for 4 h. The as-burnt powders and calcined powders were characterized with respect to phase identification, grain size and lattice parameter determination using X-ray diffraction. The sintered ferrites have been investigated for their electrical and magnetic properties such as saturation magnetization, initial permeability, AC-resistivity, dielectric constant, dielectric loss tangent as a function of zinc content. The initial permeability, saturation magnetization, dielectric constant and dielectric loss were found to increase and AC-resistivity was decreased with Zn substitution for Mg. The powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency.

Nano-crystalline copper ferrites from secondary iron oxide (mill scale)

Nano-crystalline copper ferrite compacts have been synthesized using mill scale fines via conventional oxide ceramic process. The effects of firing temperatures and time on both physical and magnetic properties of the compacts were studied. Archimedes method as well as the universal testing machine was used for determining the physical properties of the compacts. Meanwhile, the types of phase formed and the magnetic properties of the produced samples were investigated using X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. The results indicated that with a firing temperature of 1100 °C, the compact possesses higher compressive (832 kg/cm 2) strength and higher bulk density (3.93 g/cm 3), whereas higher saturation magnetization (45.2 emu/g) and lower coercivity (6.13 Oe) were achieved for compacts fired at 1200 °C. The effect of firing time at optimum firing temperature on physical and magnetic properties of the produced compacts seems to be insignificant. The crystal structure of the copper ferrite was transformed from its tetragonal into a cubic structure accompanying the dissociation of a part of the copper ferrite into delafossite at high firing temperature.