Mn-Zn Ferrite Core Research Articles

Manufacturing and performances of MnZn ferrite cores with thin walls prepared by paste material extrusion 3D printing

The 3D printing technique using material extrusion of a paste filled with ferrite powder (Mn,Zn)Fe2O4 and organic additives has been successfully improved to produce sintered samples for studying their magnetic and structural properties. The rheological behaviour of the pastes and the printing parameters have been optimised to obtain parts with regular geometries, in particular by minimising sagging effect during filament deposition. Printing is followed by a debinding and sintering stage, for which the temperature and oxygen partial pressure conditions were adjusted. These conditions enable the densification of the (Mn,Zn)Fe2O4 material in the spinel structure without parasitic phases, with a low grain size dispersion and a relative density of 91 %. The core loss has been measured on the 3D printed samples to be 144 mW/cm3 at a frequency of 500 kHz and an induction of 50 mT. This performance is comparable to the nominal value of a part produced by the conventional process. This work paves the way for an advantageous manufacturing method in terms of accessible geometries, while maintaining satisfactory magnetic characteristics.

Noise and thermal performance of a sub-attofarad capacitance sensor for precision measurements, with applications in gravitational wave detectors.

We describe the design principles, fabrication, and characterization of a precision AC resonant capacitance bridge (RCB) sensor, based on a resonant differential planar printed circuit board transformer with a solid (ungapped) MnZn ferrite core, demonstrating a short-term sensitivity at 293K of 0.225 ± 0.005 aF/√Hz at around 120kHz resonance frequency and 1Hz Fourier measurement frequency. At 120K, the RCB short term noise sensitivity is 0.118 ± 0.005 aF/√Hz. We compare the ungapped configuration to five different RCBs: three with a core gap of 65 μm and two with a core gap of 130 μm. Their average room temperature short term noise sensitivities are 0.30 ± 0.01 and 0.45 ± 0.01 aF/√Hz, while the cryogenic operation of these transformers at 120K resulted in averaged sensitivities of 0.23 ± 0.01 and 0.36 ± 0.01 aF/√Hz, respectively. Multi-hour room temperature runs, with one core of each of the three gap types, proved the stability of their long-term sensitivities of 0.234 ± 0.005, 0.338 ± 0.009, and 0.435 ± 0.010 aF/√Hz for the ungapped (40-h duration) and the 65 and 130 μm (28-h duration) cores, respectively. At 0.1mHz, a critical frequency for space gravitational wave detectors, the respective sensitivities are 0.25 ± 0.02, 0.35 ± 0.02, and 0.53 ± 0.07 aF/√Hz. Measurements with the ungapped transformer configuration for temperatures from 325 to 349K further validate the dependence of the noise model on temperature and permeability. The performance of our RCB with an ungapped core matches the calculated performance value and shows an improvement in signal-to-noise ratio of two or more compared with capacitance bridges developed for similar applications. A further factor of about two noise reductions is achieved by cooling to 120K.

Gold nanoshells with magnetic cores and a urea-based receptor for SERS sensing of fluoride anions: experimental and computational study.

The study demonstrates that a combination of plasmonic nanostructures and artificial receptors can be applied for sensing small molecular species. Gold nanoshells containing magnetic cores are used as the SERS-active substrates, which opens the way for the development of multimodal contrast agents with applicability extended to sensing or for the separation of analytes by magnetic solid-phase extraction. Disubstituted ureas forming hydrogen-bonded complexes with certain anions can be employed as molecular sensors. In this case study, gold nanoshells with silica-coated Mn-Zn ferrite cores were prepared by a multistep procedure. The nanoshells were co-functionalized with an N-(4-mercaptophenyl)-N'-(4-nitrophenyl)urea sensor synthesized directly on the gold surface, and with 4-nitrothiophenol, which is adopted as an internal standard. SERS measurements were carried out with acetonitrile solutions of tetrabutylammonium fluoride (Bu4NF) over a concentration range of 10-10-10-1 mol L-1. The spectral response of the sensor is dependent on the fluoride concentration in the range of 10-5-10-1 mol L-1. To investigate further the SERS mechanism, a model sensor, N-(4-bromophenyl)-N'-(4-nitrophenyl)urea, was synthesized and used in Raman spectroscopy with solutions of Bu4NF, up to a molar ratio of 1 : 20. The spectra and the interactions between the sensors and fluoride anions were also studied by extensive DFT computations.

Measurement Methods for High-Frequency Characterizations of Permeability, Permittivity, and Core Loss of Mn-Zn Ferrite Cores

Manganese–zinc (Mn-Zn) ferrites are the primary choice for high-frequency and high-power magnetic components. Optimum material selection is essential for high-performance magnetic component design. However, the manufacturers’ material specifications usually do not provide sufficient information to optimize the design. Complex permeability and permittivity, as well as specific power loss, are typically provided as one value, regardless of the core shape and size. Magnetic component design based on these incomplete specifications can result in a poorly optimized component. This article proposes methods to determine the properties of Mn-Zn ferrite at high frequencies, with tests up to 20 MHz. This article also presents experimental complex permeability and permittivity frequency characteristics for four ferrite materials: 3E10, 3F36, 3E65, and 3C95. The resulting fitted parameters for the equivalent-circuit model can be used in any design algorithm or simulation tool. The impacts of physical size, temperature and force on complex permeability and permittivity are also considered.

Multimodal Contrast Agent Enabling pH Sensing Based on Organically Functionalized Gold Nanoshells with Mn-Zn Ferrite Cores.

Highly complex nanoparticles combining multimodal imaging with the sensing of physical properties in biological systems can considerably enhance biomedical research, but reports demonstrating the performance of a single nanosized probe in several imaging modalities and its sensing potential at the same time are rather scarce. Gold nanoshells with magnetic cores and complex organic functionalization may offer an efficient multimodal platform for magnetic resonance imaging (MRI), photoacoustic imaging (PAI), and fluorescence techniques combined with pH sensing by means of surface-enhanced Raman spectroscopy (SERS). In the present study, the synthesis of gold nanoshells with Mn-Zn ferrite cores is described, and their structure, composition, and fundamental properties are analyzed by powder X-ray diffraction, X-ray fluorescence spectroscopy, transmission electron microscopy, magnetic measurements, and UV-Vis spectroscopy. The gold surface is functionalized with four different model molecules, namely thioglycerol, meso-2,3-dimercaptosuccinate, 11-mercaptoundecanoate, and (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, to analyze the effect of varying charge and surface chemistry on cells in vitro. After characterization by dynamic and electrophoretic light scattering measurements, it is found that the particles do not exhibit significant cytotoxic effects, irrespective of the surface functionalization. Finally, the gold nanoshells are functionalized with a combination of 4-mercaptobenzoic acid and 7-mercapto-4-methylcoumarin, which introduces a SERS active pH sensor and a covalently attached fluorescent tag at the same time. 1H NMR relaxometry, fluorescence spectroscopy, and PAI demonstrate the multimodal potential of the suggested probe, including extraordinarily high transverse relaxivity, while the SERS study evidences a pH-dependent spectral response.

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

Thermal instabilities of cobalt containing MnZn ferrite cores for medium (500 kHz) frequency applications

MnZn ferrites of the nominal composition (Mn0.81Zn0.19)Fe2.13O4, doped with cobalt, have been studied concerning the evolution of their medium (500 kHz) frequency power losses and initial magnetic permeabilities upon ageing at various temperatures for various times. Thermal ageing results to significant power loss reduction by about 50% at 400 kHz-50 mT (i.e. at 90 °C from initially 58–29 mW cm−3) and about 30% at 500 kHz–100 mT (i.e. at 90 °C from initially 690–480 mW cm−3), accompanied with a simultaneous decrease of the relative initial permeability from initially 1700–1200. The extent of power loss reduction depends on ageing time and temperature and can be described by a thermally activated process, during which Co2+ ions fall from a metastable high energy state to a stable lower energy state with an activation energy 0.33 eV/cation. Addition of TiO2 to an amount of 4000 ppm (wt.%) appears to retard the cobalt-induced ageing process by increasing the activation energy to 0.45 eV/cation, while equal amount additions of SnO2 did not seem to have any effect.

Modeling and Increasing the High-Frequency Impedance of Single-Layer Mn-Zn Ferrite Toroidal Inductors With Electromagnetic Analysis

This article first investigates the equivalent parallel capacitance (EPC) and equivalent parallel resistance (EPR) due to the electromagnetic field inside the Mn-Zn ferrite toroidal cores of the inductors with a single-layer winding based on electromagnetic theory. From the investigation, the effects of core's cross-sectional shape and number of winding turns on the EPC and EPR are explored. A stacked core structure was studied to increase the inductor's high-frequency (HF) impedance for electromagnetic interference suppression. The article further investigated the EPC due to the electric field energy in the space between winding turns, and between the winding turns and the core. The effect of the number of winding turns on total EPC was also explored. The technique to achieve high HF impedance was proposed with an optimal number of winding turns. Both simulations and experiments were conducted to validate the developed theory and techniques.

Low-power self-oscillating fluxgate current sensor based on Mn-Zn ferrite cores

A low-power open-loop self-oscillating fluxgate current sensor based on Mn-Zn soft ferrites is proposed in the paper. Differential realization of compensation amplifier, in class-D full-bridge configuration, provides full theoretical reduction of power consumption, which is impossible in the case of standard half-bridge realization. Together with data provided from the ferrite manufacturers, offered set of simple equations can qualitatively estimate quiescent and operating power consumption, and help in avoidance of design solutions that lead to unnecessary power losses. If a commercial or custom transformer core, made of conventional industrial Mn-Zn ferrite materials is used, all important parameters for sensor design, and follow-on exploitation, can be predicted in advance. Experimental examinations show that power consumption can be reduced to the level of open-loop Hall-effect based sensor, while many comparable advantages of flux-gate technology are maintained. We design sensor and tuned circuit parameters to measure currents in the range of [–20 A, 20 A] with an overcurrent capability of 50%. In temperature range of [–20 °C, 50 °C], maximum relative linearity error of 0.25% and offset drift of 0.05% is achieved.

Scheme for providing parity-time symmetry for low-frequency wireless power transfer below 20 kHz

We provided parity-time symmetry (PT symmetry) for a magnetic resonance wireless power transfer (WPT) system designed to operate below 20 kHz. A lightweight coil having a mass of 39.1 g and consisting of a Mn–Zn ferrite core and 0.6-mm-diameter copper wire is considered herein. The coil had a Q factor of 111.5 at 16.5 kHz. The proposed system oscillated at 16.5 kHz for a transmission distance of 15 mm. A transmission power of 7.6 W was achieved when the DC power supply voltage was 100 V. Under these conditions, the power efficiency between the two coils was 92.1%. The oscillation frequency was automatically tuned to the optimal frequency for obtaining the maximum efficiency for a changing transmission distance. The relationship between the transmission power and the transmission distance was very different from that of a conventional WPT system, and an effect of PT symmetry clearly appeared.

Design considerations of a fast kicker system applied in a proton therapy beamline

Abstract In a proton therapy system based on cyclotrons, a kicker magnet is an essential equipment to perform fast beam switch within 100 μ s level during energy modulation and spot scanning procedures. This paper gives a systematic view related to the design and technical considerations of a fast kicker applied to HUST-PTF. From the layout and physical requirement of the kicker, a comparative study on the static/dynamic magnetic field with two type of core materials is performed, and a MnZn ferrite core is chosen finally. Technical considerations including the structure design, the topology design of the power supply, and the method for dynamic field measurement are introduced as well.

Exploration of the 3-D Printing of Transformer Structures With Embedded Ferrite Cores

For inductor and transformer circuit components that operate at higher frequencies, the existence of parasitic capacitance due to the winding structure determines the device's self-resonance frequency. It is desirable to have precise design and manufacturing control over the winding structure to properly control this capacitance for reduced manufacturing variability, suggesting lithographic or computer numerical controlled (CNC) fabrication. Lithographic or CNC methods, however, reduce the possible number of winding turns due to the high aspect-ratio of vias, limiting the device inductance. A 3-D printing technology offers the opportunity to increase the aspect-ratio limitation by fabricating only a thin layer at one time. In this paper, the process of 3-D printing transformer structures was explored with multiple variations. A Voxel8 printer was mostly used, with the ability to print plastic as well as conductive silver paste. Commercial and custom MnZn ferrites were used as core materials, as well as printed magnetic polylactic acid (PLA) plastic using a dual-extruder MAKEiT Pro-M printer. Windings were fabricated by either silver paste deposition interleaved with plastic layers or post-fabrication silver ink injection. It was found that interleaved silver paste deposition produced very low resistance windings (high quality factor inductor) when compared with injected silver ink but had a high probability of shorting windings. Injected silver ink windings were found to have higher reliability only when the parts are properly printed liquid tight. Inductances were in agreement with theoretical predictions for most fabricated devices, and resistances were much higher for injected silver ink windings than interleaved printed windings. The best broadband transformer performance, which is an optimal low winding resistance and high mutual inductance, was found for a 36 mm outer diameter, 23 mm inner diameter, and 10 mm-thick MnZn ferrite core with an eight-turn printed winding.

Loss Simulation by Finite-Element Magnetic Field Analysis Considering Dielectric Effect and Magnetic Hysteresis in EI-Shaped Mn–Zn Ferrite Core

Loss Simulation by Finite-Element Magnetic Field Analysis Considering Dielectric Effect and Magnetic Hysteresis in EI-Shaped Mn–Zn Ferrite Core

Cobalt-Induced Performance Instabilities of Mn–Zn Ferrite Cores

Stability and reliability of transformers and inductors in power applications strongly depend on the quality of the employed ferrite cores. Given the critical role of cores, Mn–Zn ferrites’ sensitivity to their magnetic history and environmental storage conditions is investigated. To this end, Co-doped and Co-free Mn–Zn ferrites are prepared and primarily characterized in terms of structural, microstructural, and magnetic properties. The produced cores are subjected to endurance tests of technical interest comprising the response to a saturating magnetic bias and longtime storage under elevated temperature or humidity levels. With the exception of the damp heat test, prior imposition of a strong field or thermal aging process are found to induce significant instabilities to the power loss density of the Co-containing Mn–Zn ferrite cores in particular. Depending on the excitation, power loss may notably increase in the low- or high-frequency regime, whereas the effects can be either reversed with time or time independent. The proposed underlying mechanisms are based on the magnetically and thermally induced reorientation of Co2+ cations, which affects magnetocrystalline anisotropy and domain wall kinetics. Studies of different stress tests are supported by analysis of complex permeability spectra and electrical characteristics.

Influence of material uncertainties on the RLC parameters of wound inductors modeled using the finite element method

Abstract In this work, we highlight the influence of the material uncertainties (magnetic permeability, electric conductivity of a Mn-Zn ferrite core, and electric permittivity of wire insulation) on the RLC parameters of a wound inductor extracted from the finite element method. To that end, the finite element method is embedded in a Monte Carlo simulation. We show that considering mentioned different material properties as real random variables, leads to significant variations in the distributions of the RLC parameters.

Superior values of the initial permeability for electrodeposited Ni–Co–P-BaFe12O19 composite films

ABSTRACTIn this research, we detected superior values of the initial magnetic permeability for electrodeposited Ni–Co–P-M-type BaFe12O19 (BaM) composite films as magnetic soft–hard composites with a large amount of entrapped BaM particles. Furthermore, the initial magnetic permeability of Ni–Co–P-BaM composite films is significantly large and is comparable with corresponding values of the excellent corresponding values for permalloys, Sendust, Co-based amorphous alloys, nanocrystalline (Fe-based) and commercially sintered MnZn ferrite cores. Therefore, Ni–Co–P-BaM composite films are very attractive for magnetic devices, such as magnetic inductors, transformers, and magnetic recording heads.

Experimental study on the corrosion testing of a buried metal pipeline by transient electromagnetic method

Purpose This paper aims to clarify the transient electromagnetic method used for the nondestructive testing of the corrosion of an in-service buried metal pipeline in trenchless state. Design/methodology/approach The paper designed corrosion models indoor and infield for testing. A method for calculating the residual wall thickness of metal pipelines was also proposed. The calculation method was verified by the test results. In the test, the receiving probe was improved by the addition of a Mn-Zn ferrite core. The amplitudes of the test results obviously increased, and the calculation accuracy was improved. Findings The paper states that the transient electromagnetic method can detect the uniform corrosion distribution of a certain section of a pipeline. A multi-channel profile of the induced electromotive force and the calculated values of the residual wall thickness can be used to confirm the position and degree of corrosion defects, respectively. Research limitations/implications The transient electromagnetic method is more effective for large-area corrosion than for localized corrosion (pitting). Practical implications The paper includes implications for the development of nondestructive testing method of the corrosion of an in-service buried metal pipeline. Originality/value This paper proved the feasibility and reliability of using transient electromagnetic method to test the corrosion of a buried metal pipeline based on experimental study.

MnZn power ferrite with high Bs and low core loss

Although there is a tradeoff between high Bs and low core loss for MnZn power ferrite, in the current work, high Bs and a low core loss (Pcv) were achieved simultaneously by increasing the content of Fe2O3 and by adjusting the partial pressure of oxygen (PO2) during sintering process, respectively. Additionally, the influence of PO2 on the Pcv was also investigated. The MnZn ferrite cores were prepared by conventional ceramic process. With increase in PO2 from 0.35% to 1.90%, the bottom temperature of Pcv(T) curve shifted to a higher temperature, and simultaneously the minimum Pcv at the bottom temperature decreased continuously. Pcv in a low frequency range was divided into the hysteresis loss (Phv) and eddy current loss (Pev). Both Phv and Pev decreased with increasing PO2. At high PO2 cation vacancy was generated, which facilitated the transport of dopant, such as Ca and Si to the grain boundary region. This induced high resistance at the grain boundary which in turn reduced the Pev. Meanwhile, the transport of dopants from intragranular to grain boundary also reduces the defects in grains, which helped to decrease the Phv, coercivity and remanence.

Influence of losses on the output voltage of ferrite transformer in case of strong magnetic field in the core

Taking into account the nonlinear properties of ferrites the output voltage of toroidal transformer with magnetically soft ferrite core is calculated. Calculations are based on methods analogous to those used in nonlinear optics. Initially demagnetized ferrite is assumed to be isotropic. At this condition apart from the harmonic on fundamental frequency the output voltage of transformer contains also higher harmonics of odd order. Nonlinear susceptibilities of third and fifth order are used in calculations Magnetic losses are taken into account considering linear and nonlinear susceptibilities as being complex. These losses affect amplitudes of harmonics in the output voltage of transformer and create phase shifts between components of magnetization on different frequencies in the core and the intensity of exciting harmonic magnetic field. Results obtained in calculations are confirmed by experimental measurement of output voltage of toroidal transformer with MnZn ferrite core. In order to calculate amplitudes of harmonics in the output voltage of transformer numerical values of susceptibilities in question should be known.

Modeling, Design, and Fabrication of High-Inductance Bond Wire Microtransformers With Toroidal Ferrite Core

This paper presents the design of miniaturized bond wire transformers assembled with standard IC bonding wires and NiZn and MnZn ferrite toroidal cores. Several prototypes are fabricated on a printed circuit board substrate with various layouts in a $4.95\; {\rm mm} \times 4.95\; {\rm mm}$ area. The devices are modeled by analytical means and characterized with impedance measurements over a wide frequency range. Experimental results on 1:38 device show that the secondary self-inductance increases from 0.3 μH with air-core to 315 μH with ferrite core; the coupling coefficient improves from 0.1 with air-core to 0.9 with ferrite core; the effective turns ratio enhances from 0.5 with air-core to 34 with ferrite core. This approach is cost effective and enables a flexible design of efficient micromagnetics on top of ICs with dc inductance to resistance ratio of 70 μH/Ω and an inductance per unit area of 12.8 μH/mm2 up to 0.3 MHz. The design targets the development of bootstrap circuits for ultralow voltage energy harvesting. In this context, a low-voltage step-up oscillator suitable for thermoelectric generator sources is realized with a commercial IC and the proposed microtransformers. Experimental measurements on a discrete prototype report that the circuit bootstraps from voltages down to 260 mV and outputs a dc voltage of 2 V.