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The performance and efficiency of high-frequency transformers (HFTs) are significantly influenced by leakage inductance. To improve the efficiency of HFTs, it is crucial to consider the effects of leakage inductance during the design and analysis processes. This research study aims to investigate a high-frequency toroidal transformer by examining different magnetic materials (Ferrite, Amorphas, and Iron-Powdered Alloy), winding configurations (solid, twisted, and LITZ wire), and operating frequencies (10 kHz and 50 kHz). To validate the effectiveness of parametric optimization in enhancing the system efficiency, the designed toroidal HFT was constructed and tested in a 600/300 V 3 kW dual active bridge (DAB) converter. The leakage inductances were measured using a frequency sweeping LCR meter. [ABSTRACT FROM AUTHOR]

Cryogenic isolators play an important role in low-noise receiver systems widely employed in millimeter and submillimeter telescopes. To enable a significantly wider Intermediate Frequency (IF) bandwidth, there is strong demand for a wideband, low-loss isolator in modern facilities like the Submillimeter Array (SMA) and Atacama Large Millimeter/submillimeter Array (ALMA). In this article, we present a novel cryogenic edge-mode isolator that incorporates an innovative circuit design. Operating at a cryogenic temperature of 4 K, this isolator delivers unprecedented performance, covering a frequency range from 4 GHz to 22 GHz. It exhibits insertion loss of less than 1 dB, together with return loss below -15 dB. In particular, it provides an isolation better than 17 dB across most of the band, a significant improvement over the previous generation of edge-mode isolators. This new isolator design is suitable for a wide array of low-noise receiver applications, from radio-astronomy to quantum computing.

Integration of the ferrite devices in the RF front-end and active antennas is hindered by the need for external magnets, biasing soft microwave ferrites. The hexaferrite-based self-biased nonreciprocal devices can operate without external magnets at mm-wave frequencies but the currently available hexaferrite materials inflict high RF losses at lower frequencies, particularly in the wireless communication bands. In this paper, the parameters of La-Co-substituted hexaferrite compounds are used for the self-biased circulators in the low GHz frequency bands, and a means of the dissipation loss reduction are discussed. [ABSTRACT FROM AUTHOR]

Abstract The contribution of this work is to propose a novel circulator design using the substrate‐integrated coaxial line (SICL) structure. Conventionally, the circulator is composed of three‐dimensional waveguide components, and, in contrast, the proposed SICL circulator allows the 3‐D waveguide circulator to be built in a planar form using the printed circuit board (PCB) technology. The proposed SICL circulator is composed of three substrates with two parallel signal strips embedded in the central SICL tunnel. For better impedance matching, a widened section is inserted in each uniform feedline, and the Y‐junction joint on the bottom surface of the middle substrate is connected with three stubs and is loaded with a circular disk on the top surface of the middle substrate. A bandpass filter (BPF) can be embedded in each circulator's branch to improve signal selectivity and the out‐of‐band isolation. Experiments are conducted to verify the circuit design. Agreements are observed between the measured and simulated data.

Traditional predicted core loss models, such as the improved Steinmetz equations, cannot show the whole changing tendency of core losses in different topologies. In this article, a core loss prediction model is presented based on sinusoidal losses. The axis of flux density is divided into a number of slice pairs in a B-Ph plane, and the hysteresis loss density is given in each slice pairs. By summing hysteresis losses associated with the actual swings of flux density in the B-Ph plane, total hysteresis losses can be calculated quantitatively. This empirical approach is available both in calculating hysteresis losses under the centered and noncentered minor hysteresis loops. The effect of duty cycles on the swings of flux density and dc bias are analyzed, and two terms of kdc(D) and kΔB(D) are identified to show their effects on hysteresis losses. Dynamic eddy current losses are mainly associated with exciting waveforms, which are indicated by introducing a term ke(D). Since the main features of power converters are characterized by three terms, the behaviors of core losses in various topologies can be described adequately. Experimental results from three typical power converters agree with theoretical analyses well. [ABSTRACT FROM AUTHOR]

The contribution of this work is to propose a novel circulator design using the substrate‐integrated coaxial line (SICL) structure. Conventionally, the circulator is composed of three‐dimensional waveguide components, and, in contrast, the proposed SICL circulator allows the 3‐D waveguide circulator to be built in a planar form using the printed circuit board (PCB) technology. The proposed SICL circulator is composed of three substrates with two parallel signal strips embedded in the central SICL tunnel. For better impedance matching, a widened section is inserted in each uniform feedline, and the Y‐junction joint on the bottom surface of the middle substrate is connected with three stubs and is loaded with a circular disk on the top surface of the middle substrate. A bandpass filter (BPF) can be embedded in each circulator's branch to improve signal selectivity and the out‐of‐band isolation. Experiments are conducted to verify the circuit design. Agreements are observed between the measured and simulated data. [ABSTRACT FROM AUTHOR]

In this paper, a wideband directional coupler is proposed for high‐power applications, which is composed of a transformer and lumped elements. The introduction of the transformer greatly improves the directivity of the coupler. The measurement results demonstrate that the proposed design has an excellent return loss (>17 dB), small insertion loss (<0.4 dB), and high directivity (>22) over a wide frequency band (10–350 MHz). Meanwhile, it can achieve a flat coupling level of 32 dB with the imbalance less than 0.5 dB. [ABSTRACT FROM AUTHOR]

We theoretically investigate the formation of hotspots at microwave frequencies in a partially filled, ferrite-loaded rectangular waveguide. When the unidirectional mode of this waveguide approaches an impenetrable conducting barrier, its magnetic field rises sharply due to the absence of reflection. To study this phenomenon, we use the magnetostatic approximation and derive a surface integral equation for the normal component of magnetic flux density on the surface of the ferrite layer. For a half-filled waveguide, an analytic solution is found, which shows the magnetic field to diverge near the barrier as |x|-q, where |x| is the distance from the barrier edge and q is slightly less than unity. For filling factors other than one-half, the numerical solution of the surface integral equation again confirms the appearance of a hotspot near the barrier edge. [ABSTRACT FROM AUTHOR]

The wetting and brazing of Y3Fe5O12 (YIG) ceramics with a Ag–8CuO–2TiO2 filler was investigated for the first time. For comparison, the wettability of a Ag–10CuO filler on YIG ceramics was similarly investigated. The Ag–8CuO–2TiO2 filler has an equilibrium contact angle of approximately 31 °C on the YIG substrate at 1000 °C; thus, its wettability is excellent. Moreover, its wettability exceeds that of Ag–10CuO. The microstructure and the interfacial structure between the filler and the substrate were determined using scanning electron microscopy, X-ray diffraction, EPMA and transmission electron microscopy. The liquid Ag–8CuO–2TiO2 filler can react with the YIG substrate by forming continuous Y2Ti2O7 layers with dotted CuFe2O4 and promote the wetting behavior and bonding performance. The average shear strength could exceed 30 MPa for the joints at a brazing temperature of 1000 °C. As rupture occurred adjacent to the seam at the ceramic side, the strengths of the interfaces were characterized via nanoindentation. The hardness of the interface with doped TiO2 exceeds that of Ag–10CuO, which is strengthened by the dotted CuFe2O4 among Y2Ti2O7.

This article describes a new set of tools developed to improve the conception and modeling of nonsaturated ferrite-based devices such as twin toroid phase shifters. These new simulation tools benefit from a generalized permeability tensor model able to describe the permeability tensor of a ferrite sample whatever its magnetization state. This model is coupled to a homemade 3D multi-scale magnetostatic analysis program, which describes the evolution of the magnetization through the definition of a hysteresis loop in every mesh cell. These computed spectra are then integrated into 3D electromagnetic simulation software that retains the spatial variations of the ferrite properties by using freshly developed macro programming functions. This new approach allows the designers to accurately model complex ferrite devices such as twin toroid phase shifters. In particular, we demonstrated a good agreement between simulated and measured phase shifts as a function of applied current values with a predicted maximum phase shift of 0.96 times the measured value. [ABSTRACT FROM AUTHOR]

A magnetically tunable metamaterial perfect absorber (MPA) based on ferromagnetic resonance is experimentally and numerically demonstrated. The ferrite-based MPA is composed of an array of ferrite rods and a metallic ground plane. Frequency dependent absorption of the ferrite-based MPA under a series of applied magnetic fields is discussed. An absorption peak induced by ferromagnetic resonance appears in the range of 8–12 GHz under a certain magnetic field. Both the simulated and experimental results demonstrate that the absorption frequency of the ferrite-based MPA can be tuned by the applied magnetic field. This work provides an effective way to fabricate the magnetically tunable metamaterial perfect absorber. [ABSTRACT FROM AUTHOR]

The nanocomposites, consisting of BaFe12O19 ferrite and few-layer graphene sheets (FL-GSs) in various weight ratios (1--9 wt. %), were fabricated by a mechanical mixing method. The high-crystalline FL-GSs were prepared by direct current arc discharge evaporation of pure graphite electrodes in an H2-Ar gas mixture. We measured the electromagnetic properties, including effective magnetic permeability and effective permittivity in addition to microwave absorption performance, of the FL-GSs/BaFe12O19 nanocomposites compared with the pristine BaFe12O19 nanoparticles (NPs). The nanocomposite FL-GSs/BaFe12O19 with the optimal performance (6 wt. % FL-GSs) exhibited an effective microwave absorption (<-10 dB) bandwidth of 5.8 GHz with a thickness of 2.2 mm, 53% higher than that of the pristine BaFe12O19 NPs. Meanwhile, this nanocomposite had the minimum reflection loss of -49.7 dB at 8.4 GHz with a thickness of 2.8 mm, three times greater than those without FL-GSs. These performances result from a simultaneous increase in both magnetic and dielectric losses possibly due to synergistic effects of BaFe12O19 and FL-GSs. In such nanocomposites, both magnetic loss from BaFe12O19 and dielectric loss from FL-GSs contribute to the absorbing performances. Adding FL-GSs as dielectric fillers enhances the impedance matching of the nanocomposites compared with the pristine BaFe12O19 NPs based on the magnetic loss alone. Our results indicate that the incorporation of high-crystalline nanocarbon materials into ferrite oxides can provide high microwave absorption intensity and broad effective absorption bandwidth, while maintaining high thermal stability. [ABSTRACT FROM AUTHOR]

Two-degree-of-freedom control of field distribution on the pseudotraveling wave resonator using nonreciprocal metamaterial lines is demonstrated for the first time. Dynamic control of current distribution on the resonator is given based on circuit theory. We employed a normally magnetized ferrite microstrip line-based composite right-/left-handed (CRLH) transmission line as a metamaterial with variable phase-shifting nonreciprocity. Numerical simulation results show that the phase gradient of the fields along the resonator is controlled by the applied dc magnetic field to the ferrite. By changing the reflection coefficients of two reflectors inserted at both ends of the CRLH line section, current distribution along series and shunt branches of the unit cell is continuously and drastically changed under the resonance. The variable field distribution was implemented to polarization-plane-rotation and beam-scanning leaky-wave antennas. The experimental demonstration verifies our basic concept and shows the performance of the prototype antenna with a beam scanning angle of 20° and a continuous rotation angle of polarization plane by ±70° at the fixed frequency. [ABSTRACT FROM AUTHOR]

We report on the structural, temperature, and frequency dependent impedance studies of Ti doped cobalt ferrite material (CoFe1.95Ti0.05O4) in comparison with the pure CoFe2O4. XRD and Raman spectroscopy studies confirm the inverse spinel crystallization of the materials with space group of Fd-3 m. Scanning electron microscope images shows the microcrystalline nature of the particles. Homogeneity, stoichiometry, and ionic states of the ions in the composition were confirmed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopic studies. Temperature and frequency dependent real (Z') and imaginary (Z") part of the impedance shows the existence of relaxation processes and their distribution in CoFe2O4 and CoFe1.95Ti0.05O4 materials. Complex impedance spectroscopy studies at low temperatures shows that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. Room temperature total dc conductivity of both CoFe2O4 and CoFe1.95Ti0.05O4 materials is found to be 5.78×10-8 and 1.61×10-7 S/cm, respectively. Temperature variation of dc electrical conductivity follows the Arrhenius relationship and the activation energies for CoFe2O4 corresponding to grain (0.55 eV for CoFe2O4), grain boundary (0.52 eV), and total conduction (0.54 eV) are discussed. Observation of well distinguishable grain and grain boundary conductions and the low conductivity values in CoFe2O4 and CoFe1.95Ti0.05O4 materials indicates that these materials are promising candidates for the high frequency applications. [ABSTRACT FROM AUTHOR]

This study proposes a special topology of transvers flux permanent magnet generator, which benefits from low Permanent Magnet (PM) costs due to use of cheap Ferrite PMs. In this structure, only one PM per phase is used to ensure easy manufacturing. Despite the above-mentioned advantages of the topology, it is subject to some disadvantages such as unbalanced voltage, high demagnetization risk of the PM, and high cogging torque. Aiming to solve these problems and maintaining the advantages of the topology, a new structure is proposed. The stator of this structure contains two series connected coils that eliminate all the even-order harmonics and balance the voltage waveform. This trick reduces the armature reaction as well as demagnetization of the PMs significantly. Moreover, the rotor teeth of the proposed structure are skewed, causing a significant reduction in cogging torque. The output results of the proposed structure are compared with those of the original one in terms of harmonic components, cogging torque profile, and PM demagnetisation. [ABSTRACT FROM AUTHOR]

Spinel ferrite Ni0.5Zn0.3Co0.2Fe1.98O4-x nanoparticles were synthesized by co-precipitation method, and samples were realized by moulding and annealing at key temperatures (TM=800°C, 900 °C, 1050 °C, determined beforehand through shrinkage measurements) going with calcining and sintering processes. Annealing at 800 °C and 900 °C led to half-dense ceramics (porosity ∼50 vol. %), whereas bulky ferrite was obtained after annealing at 1050 °C. Elemental analysis, X-ray diffraction and ion chromatography analysis were performed. Complex dielectric permittivity (ε*) and magnetic permeability (μ*) were investigated up to 6 GHz. With increasing TM, a decreasing amount of Fe2+ was observed, going with increasing sample density. Coupled effects of the Fe2+ concentration and of the porosity, both on dielectric and magnetic properties, were chiefly investigated and discussed. The materials show almost constant permittivities (ε' =5.0, 6.0, and 14.8 for TM=800 °C, 900 °C and 1050 °C, respectively). The bulk value at f=1 GHz (ε' =14.8) can be interpreted well according to Shannon's theory. The permittivities of the half-dense ceramics are discussed on the basis of Bruggeman's Effective Medium Theory. The materials annealed at 800 °C and 900 °C show almost constant magnetic permeabilities in the frequency range from 0.2 to 1GHz (μ' =3.4 and 6.0 for TM=800 °C and 900 °C). The observed permeability behavior is typical of monodomain particles, except for the sample annealed at 1050 °C, for which domain wall contribution to μ* is suspected because of non-negligible losses at low frequency (μn =1.3-1.8 at f<0.3 GHz). This finding is supported by estimations of the upper and lower values for the critical grain size, on the basis of Brown-Van der Zaag's theory. Facing bulk ceramics, and in view of using Ni0.5Zn0.3Co0.2Fe1.98O4-x ferrite as substrate for antenna miniaturization, the electromagnetic properties of half-dense ceramics materials seem to be very competitive at frequencies beyond 0.2 GHz, and up to 0.7-0.8 GHz. [ABSTRACT FROM AUTHOR]

Roadway inductive power transfer presents an opportunity to provide a robust and user friendly system for electric vehicle charging by utilizing magnetic couplers (pads) embedded in the roadway. Roadway pads are expected to have a long service life but existing pads use a large quantity of the brittle magnetic material ferrite, which may break in the harsh environment of a roadway. This article shows what happens when the volume of ferrite material is reduced from an example double D pad to minimize the quantity and size of ferrite that needs to be protected. Also presented are design insights into the placement of a reflection winding that helps shape the field in the absence of the majority of ferrite. The final selected example design reduces the leakage magnetic field where a person may be present by 43%, at the expense of an increase in primary VA of 73% from the original double D pad. The final presented pad reduces the ferrite volume by 86% compared to the original example double D pad, is only 50 mm thick, and is shown to have a measured dc–dc efficiency of 91% when delivering 4.7 kW to an available secondary. [ABSTRACT FROM AUTHOR]

Due to the multipactor discharge breakdown, ferrite circulators have become the most susceptible component losing efficacy in high-power applications such as satellite payload systems. To date, effective suppression method of multipactor without affecting the electrical performance while keeping a high level of stability during in-orbit operation is still a technological challenge. In this article, a novel method based on the composite dielectric transformation is proposed for the considerable improvement of the multipactor breakdown threshold. The transformation medium is composed of dielectric rings of different permittivity, which could realize the uniform field transformation from the susceptibility region of multipactor to the dielectric/vacuum interface without acute change and discontinuity. In addition, the transformation medium is designed to guarantee little perturbance of the electrical performance and great convenience of fabrication and assembly. The experimental results of the S-band circulator using this method demonstrated that while keeping very low insertion loss and isolation level, this method has improved more than 9 dB (≥ 850%) of multipactor threshold, showing very promising application potentials in antimultipactor designs for the spacecraft payload system. [ABSTRACT FROM AUTHOR]

This article presents the design and fabrication of a microstrip $C$ -band microwave isolator using additive technology. Such fabrication requires multimaterial 3-D printing (dielectric and absorber) and the embedding of ferrite ceramic inside the substrate. First, our design demonstrated that an efficient microstrip load can be made by 3-D printing in a single process: not only the dielectric but also the absorber, which takes the form of steps in the substrate. Then, a circulator with a composite dielectric/ferrite resonator was designed. Finally, circulator and load were integrated in a single component to optimize the isolator. The device was then 3-D-printed with a pause during the fabrication to allow the ferrite disk to be embedded. Microwave measurements demonstrated that minimum insertion losses of 0.76 dB were achieved, together with a −15 dB bandwidth of 11.9%. To our knowledge, this is the first demonstration of the feasibility of fabricating a non-reciprocal microwave component by additive technology. [ABSTRACT FROM AUTHOR]

The application of smart electronic instruments to detect leakage of inflammable or poisonous gases in the environment has significant importance in agricultural, industrial, smart home, and domestic applications. Detecting LPG through an early warning system at home, hotels, restaurants, and LPG warehouses can prevent fire accidents and save lives and avoid economic losses. Recent developments in digital electronics technology are more reliable in designing smart electronic systems to sense gas, and measure its concentration numerically. Using the AVR Atmega16 microcontroller on-chip tools, an electric nose design has been developed to detect LPG leakage. For present system, LPG sensor Figaro 813 and ferrite based sensor interfaced with on-chip ADC of AVR microcontroller has been used. It has a high level of agreement with the actual values and can detect the presence of LPG due to a leakage. In this paper, the results of both sensors are interpreted. The device is primarily intended to assist and enhance the security of smart kitchens. [ABSTRACT FROM AUTHOR]

It is widely recognized that as electronic systems' operating frequency shifts to microwave and millimeter wave bands, the integration of ferrite passive devices with semiconductor solid state active devices holds significant advantages in improved miniaturization, bandwidth, speed, power and production costs, among others. Traditionally, ferrites have been employed in discrete bulk form, despite attempts to integrate ferrite as films within microwave integrated circuits. Technical barriers remain centric to the incompatibility between ferrite and semiconductor materials and their processing protocols. In this review, we present past and present efforts at ferrite integration with semiconductor platforms with the aim to identify the most promising paths to realizing the complete integration of on-chip ferrite and semiconductor devices, assemblies and systems. [ABSTRACT FROM AUTHOR]

The effects of a demagnetizing field and an external static magnetic field on the effective Snoek’s product of textured Z-type hexagonal ferrite, which is the product of effective susceptibility and resonance frequency, were examined in order to apply the Z-type hexagonal ferrite to high-frequency devices. As a result, the demagnetizing field due to the thin plate geometry increased the resonance frequency and the effective Snoek’s product when a high-frequency magnetic field was applied parallel to the c-plane of the Z-type hexagonal ferrite. Moreover, the resonance frequency, effective susceptibility, and effective Snoek’s product of 7.7 GHz, 10.7, and 82.2 GHz, respectively, were obtained when an external magnetic field that was sufficient to saturate the Z-type hexagonal ferrite slab was applied parallel to the c-plane and perpendicular to the high-frequency magnetic field. Furthermore, the Landau–Lifshitz equation suggested that a large Snoek’s product of over 50 GHz could be obtained with an external static field as small as 31 kA/m, which is enough to saturate the Z-type hexagonal ferrite. [ABSTRACT FROM AUTHOR]

The reflection of a normally incident plane wave due to the interface between vacuum and a Faraday chiral medium (FCM) supported by a perfect electric conductor was rigorously derived. Numerical results strongly indicated that arbitrary polarization conversions are realizable from the incident plane wave to the reflected plane wave by properly choosing the constitutive parameters of the FCM. [ABSTRACT FROM AUTHOR]

The effects of hydrostatic pressure on the magnetism, capacitance, and impedance of a manganese zinc ferrite device have been investigated. Giant piezomagnetism, piezocapacitance, and piezoimpedance that are independent of skin effects have been observed simultaneously under a pressure of a few megapascals. With increasing frequency of the current applied across the ferrite device, these pressure effects have been found to undergo a maximum at a frequency below 3 kHz. Under a pressure of 6 MPa, a piezoimpedance over 60% has been observed for the ferrite devices with permeabilities ranging from 5000 to 15 000. Analysis shows that these pressure effects result from the variation of the interior stress in the ferrite. [ABSTRACT FROM AUTHOR]

Conventional electronic article surveillance (EAS) tags are ineffective on metallic packaging. The component of the RF magnetic field perpendicular to the surface of the packaging induces eddy currents that suppress the magnetic flux, linking the inductive element of the tag. In this article, an inductive quarter-wavelength planar cavity, formed by wrapping aluminum foil around a ferrite core, was extended by wrapping additional capacitive layers of foil/dielectric around the ferrite-filled central region. This so-called wrapped tag exhibits the frequency, $Q$ -factor, and read distance characteristics of existing EAS tags, but is instead driven by the RF magnetic fields parallel to the surface of the metallic packaging. In this article, we compare the observed frequency response of the wrapped tag with a simple LC resonator model that considers the tag’s geometrical features, and use the model to describe how the design and construction of the tag can be optimized. Finite-element method (FEM) modeling is used to reveal how the current flows in the wrapped foil of the tag. Prototype tags show good reproducibility, demonstrating the potential of the design as a solution to the problem of tagging metallic packaging in the EAS industry. [ABSTRACT FROM AUTHOR]

Abstract Deformation response of DP1200 steel was studied under high strain rate. Ferrite cracking occurs when strain rate exceeds the critical range (500–700 s−1). Cracks in ferrite propagate to martensite/ferrite interface, weakening its inhibitory effect on adjacent martensite. Thus martensitic deformation becomes the main factor of total deformation earlier to enhance the total strength. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review on the synthesis and stability of ferrite nanoparticles such as nickel ferrite (NiFe2O4), zinc ferrite (ZnFe2O4), manganese ferrite (MnFe2O4), iron ferrite (Fe2O3), cobalt ferrite (CoFe2O4) and also mixed nanoparticles. Different synthetic methods for ferrite nanoparticles have been reviewed such as co-precipitation, thermal decomposition and hydrothermal, microwave-assisted and sonochemical methods. The effect on the stability of different capping agents like canola oil, glycerol, sodium dodecyl, sodium citrate, oleic acid, Triton-100 and sodium dodecyl benzene sulfonates has also been studied. [ABSTRACT FROM AUTHOR]

Abstract The influence of tensile stress on hysteresis loop of Reduced Activation Ferrite & Martensitic steel (RAFM steel) in elastic region was quantitatively evaluated through experiments in this paper. In view of in vessel structures of the RAFM steel in the Tokamak devices, the variation of magnetic material properties caused by forces or mechanical deformation may lead to unexpected influences on their dynamical behaviors, even safety problem. In this paper, tensile experiments of a RAFM steel were conducted under magnetic field up to 60 kA/m to measure its hysteresis loops under different tensile stress. Tensile specimens of a RAFM steel developed in China (CLAM steel) were fabricated and measured with a multi-field coupling experimental system. The maximum relative permeability under different experimental conditions was extracted from the measured hysteresis loops. Experimental results show that a clear variation of the maximum magnetic permeability was observed when the external tensile stress was enlarged. In addition, based on a linear theory of magneto-solid coupling mechanics, a model of constitutive relation between tensile stress and maximum magnetic permeability was put forward and validated based on the experimental results. [ABSTRACT FROM AUTHOR]

Ethernet transformers are mass produced broadband signal coupling transformers, used for interfacing copper twisted-pair networking cable to Ethernet devices. In this paper, we present a process for fabricating Ethernet transformers by embedding ferrite core materials within printed circuit board, and then fabricating the windings around the embedded core. Sample transformers were fabricated with different winding configurations and core materials. It is then possible to clad the board with copper and fabricate routes or mount components to the board faces, making the transformer a zerofootprint component. The sample transformer's performance is experimentally evaluated, and the results are presented in this paper. All transformers were found to successfully couple up to 1000Base-T Ethernet. [ABSTRACT FROM AUTHOR]

Two screen printing inks were developed for the low-temperature fabrication of printed and flexible thick film negative temperature coefficient thermistors able to operate at room temperature. The first of the two screen printing inks developed utilised cobalt ferrite (CoFe2O4) as the temperature sensing material with the second ink incorporating manganese ferrite (MnFe2O4). These were then screen printed onto lithographically printed silver interdigitated electrodes with a 200 µm track and gap using a synthetic paper (Teslin) as the substrate. The inks required a 10 min curing step at 80°C. Pre-annealing of the ferrite powders before ink formulation enabled the avoidance of high-temperature processing post-fabrication typically required in industrial thermistor production. The printed thermistors were tested at a controlled constant humidity between 15 and 50°C. Both materials demonstrated typical natural logarithmic responses with high linearity and sensitivity. [ABSTRACT FROM AUTHOR]

Abstract The design of high-strength martensitic stainless steels requires an accurate control over the stability of undesired phases, like carbides and ferrite, which can hamper strength and ductility. Here, the ferrite to austenite transformation in Fe-11Cr-0.06C has been studied with a combined experimental-modelling approach. Experimental observations of the austenization process indicate that austenite growth proceeds in multiple steps, each one characterized by a different transformation rate. DICTRA based modelling reveals that the dissolution of the M 23 C 6 Cr-rich carbides leads to Cr partitioning between austenite and parent phases, which controls the rate of transformation through (i) a soft-impingement effect and (ii) consequent stabilization of the ferrite, which remains untransformed inside chromium-enriched-zones even after prolonged austenization stage. Slow heating rate and smaller initial particle sizes allow the design of ferrite-free microstructure. Graphical Abstract Highlights • The microstructure design of stronger martensitic stainless steels hinges on austenization kinetics. • Cr-rich carbides controls the transformation kinetics due to Cr partitioning and stabilization of ferrite. • Coarse carbides and fast heating rates lead to a soft-impingement of the Cr diffusion fields ahead of austenite interface. • Ferrite-free microstructures can be produced for slow heating rate or smaller initial carbides. [ABSTRACT FROM AUTHOR]

Abstract Strontium hexaferrite single crystals, SrFe 12 O 19 , with sizes of up to 5 mm were grown by spontaneous crystallization from sodium oxide based flux. The structural and morphological characterization of the grown samples was performed by powder and single crystal X-ray diffraction and scanning electron microscopy, respectively. X-ray diffraction reveals that all prepared samples are single-phase with magnetoplumbite structure. The unit cell parameters were determined to a = 5.8832(4) Å, c = 23.0361(14) Å, V = 690.51(6) Å3. Magnetic hysteresis curves on single crystals reveal an almost ideal soft magnetic behavior, whereas a ground sample shows an increased value for the coercivity. [ABSTRACT FROM AUTHOR]

This paper presents the design considerations in cogging torque minimization in two types of transverse flux machines. The machines have a double stator-single rotor configuration with flux concentrating ferrite magnets. One of the machines has pole windings across each leg of an E-Core stator. Another machine has quasi-U-shaped stator cores and a ring winding. The flux in the stator back iron is transverse in both machines. Different methods of cogging torque minimization are investigated. Key methods of cogging torque minimization are identified and used as design variables for optimization using a design of experiments (DOEs) based on the Taguchi method. A multilevel DOE is proposed as an optimization method to reach an optimum solution with minimum simulations. The case study is analyzed in a two-level DOE optimization. Finite element analysis (FEA) is used to study the different effects. Two prototypes are fabricated for validating the FEA results. [ABSTRACT FROM AUTHOR]

Abstract In order to ensure that appropriate tempering conditions are used to obtain desired strength and toughness for low carbon low alloy quench and tempered (Q&T) steel plates in a range of thickness, it is desirable to be able to predict the effect of composition and tempering conditions (time and temperature) on the microstructure and hence the hardness evolution for these steels. In this paper, carbide precipitation and coarsening behaviour in three low carbon low alloy Q&T steels have been investigated during tempering at 600 °C up to 16 h to determine the role of alloying additions of Mo, V, Cr and Si. It has been found that auto-tempering occurs during water quenching with ε'-carbide and cementite being present within the martensite laths for all three steels. In the Base steel, cementite becomes the stable second phase after 2 h tempering and has an elliptical (sometimes spherical) shape, which coarsens with time during tempering from 2 h to 16 h. However, in the Base-Mo-V and Base-Cr-Mo-V-Si steels, elliptical and needle-shaped cementite (shown to contain Mn, Mo and Cr) both exist during tempering; furthermore, finer elliptical secondary Mo-V-rich carbides are observed after tempering for 4 h. The coarsening of cementite contributing to the softening process in the three steels has been quantified with, most significantly, the inter- and intra-lath carbides coarsening independently. Although fine secondary alloy carbides are observed after 4 h tempering, they do not result in any noticeable secondary hardening peak in the Base-Mo-V and Base-Cr-Mo-V-Si steels. [ABSTRACT FROM AUTHOR]

This paper investigated the magnetic properties of novel soft magnetic composite (SMC) with ferrite nanofibers. Material consists of FeSi powder covered by resin and different amounts of Ni0.3Zn0.7Fe2O4ferrite nanofibers. We prepared SMC with very high specific electrical resistivity. FeSi/resin (0.49 wt% ferrite) sample exhibits the highest electrical resistivity ($6.05~\Omega \cdot \text{m}$) due to low interparticle contacts. The image analysis of SEM pictures was used for the evaluation of effective area, in which local eddy currents are flowing. The FeSi/resin (0.49 wt% ferrite) sample displays the lowest total losses in the measured frequency range due to the highest specific electrical resistivity and appropriately covered FeSi particles. Loss separation and the analysis of movable magnetic objects were performed for all studied materials. [ABSTRACT FROM AUTHOR]

Abstract Three austenitic stainless steel welds (ASSW), such as E308, ER316L and ER347, with about 10% of δ-ferrite were thermally aged at 400 °C up to 10000 h to accelerate the thermal ageing expected in pressurized water reactor (PWR) environment. Fluctuation of Fe and Cr due to spinodal decomposition is observed with width of 5–12 nm within the ferrite phase. For all 3 welds, increase in strength and decrease in tensile elongation is observed after thermal aging at room temperature and 320 °C. The reduction in fracture resistance, measured as J-R curves, is most significant for ER316L weld with decrease by about 50%. However, it is quite small (about 10% decrease) for ER347 weld even after ageing at 400 °C for 10000 h despite the large reduction in tensile elongation. Finally, the double loop-electrochemical potentiodynamic reactivation (DL-EPR) tests show the degree of sensitization (DOS) values are negligible even after the accelerated thermal ageing at 400 °C for 10000 h. [ABSTRACT FROM AUTHOR]

This paper presents the design of dual-port subarray modularization integrating a three-port circulator, realized by using substrate integrated waveguide (SIW) technology, and a subarray of antenna elements for dual uplink and downlink beamforming. In particular, a $2\times2$ element module is implemented and fabricated on a standard printed circuit board substrate to demonstrate its radiation characteristics and operational mechanism. In this design, the SIW structure is used to reduce the radiation from microstrip lines at millimeter-wave frequencies and avoid contaminating the radiation patterns of subarrays. Greater than 5 dBi suppression has been achieved for good compatibility with the integration of radio frequency devices. The measured results show that the subarray modularization improves the insertion loss and results in an excellent isolation for independent transmitting and receiving beamforming network implementation. Numerical and experimental results are shown to verify the performance of these designs. [ABSTRACT FROM AUTHOR]

Abstract The present report deals with the structural and elastic behavior of Li+ and Zr4+ substituted spinel ferrites. Nanocrystalline spinel ferrite system of chemical formula Li 0.5+0.5x Zr x Fe 2.5-1.5x O 4 (where, x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) was synthesized by using sol-gel auto combustion method. The as-prepared powder was annealed at 800 °C for 5 h for better crystallinity. The annealed samples were characterized by X-ray diffraction technique and Fourier transform infrared spectroscopy for structural and elastic studies respectively. By applying the full pattern fitting of Rietveld method the x, y, z coordinates of atoms, unit cell dimensions and occupancy of ions were estimated. The lattice parameter was found to decrease after substitution due to increase in electron affinity. Site preferences of cations were obtained by matching experimental and calculated intensity. The characteristic bands of crystallographic sub-lattice for the cubic structure were observed by FTIR spectra. Highlights • The monovalent and tetravalent substitution in spinel ferrite was successfully done by sol gel autocombution technique. • Good nanocrystalline spinel ferrite material was achieved by simple and cost effective synthesis technique. • The ordered inverse spinel structure of Li 0.5 Fe 2.5 O 4 is not influenced by Zr4+ substitution. • The cation distribution suggest that the Zr4+ ions prefer octahedral [B] site. • The elastic properties were estimated by Furrier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Mn-Ni-Zn ferrite with the chemical formula of Mn0.2Ni0.3Zn0.5Fe2O4 was prepared by co-precipitation method. The X-ray diffraction (XRD) results show that the prepared sample crystallizes in the cubic spinel structure with the space group of Fm3m. The morphological analysis of the sample was investigated by scanning electron microscopy (SEM). The dielectric properties of Mn0.2Ni0.3Zn0.5Fe2O4 ferrite were studied in a frequency range from 20 Hz to 10 MHz and at a temperature range from 293 to 733 K. The dielectric constant decreases with the increasing frequency for all the temperature values chosen. The AC conductivity mechanism was found the small polaron type of conductivity, and in addition to that, the DC conductivity can be explained by Arrhenius type conductivity. According to the dielectric results, relaxation process fits Cole-Cole model. Finally, the effect of the relative humidity upon the impedance of the sample was discussed for a frequency range between 20 Hz and 10 MHz. It is found that the impedance values decrease almost linearly with the increasing % RH (relative humidity) values at low frequencies, while the impedance of the sample is independent of % RH at high frequencies. [ABSTRACT FROM AUTHOR]

In this present paper, failure analysis is conducted for a pipe used in fire water applications. In petroleum industries many failures were observed in API 5 L grade steel pipes. The past inspection history records were observed, which reveals that failed pipeline is poorly maintained since construction. Visual inspection, macroscopic and microscopic examinations were conducted for the failed pipe. The microscopic analysis reveals that the pitting corrosion is a root cause of failure which perforates the wall thickness at 6′o′ clock pipe position. The mechanism of pitting corrosion is correlated with ferrite matrix dissolution. The Cu, Co & Zn ions were detected in scale deposits reveals that the fire water is severely contaminated by various makeup water sources which results in under deposit corrosion. The various sources of foreign elements are discussed in detail. The copper deposits identified at suspected location attributed to galvanic corrosion. Moreover, the severity of pitting is aggravated by grain boundary attack which acts as an anode during corrosion process. Based on various experimental evidences, the conclusions were drawn and further recommendations are discussed to mitigate the corrosion failure. [ABSTRACT FROM AUTHOR]

The strength-toughness combination of an ultra-low carbon, low alloyed ‘air-cooled’ steel has been enhanced by developing and refining the granular bainite (GB) structure. Suitable alloy design and thermo-mechanical treatment involving forging, austenitisation (950-1150°C) and air-cooling resulted in the formation of GB matrix along with small islands of martensite-austenite constituents and allotriomorphic ferrite grains. Microstructural characterisation and phase transformation behaviour were studied by scanning electron microscopy and electron backscattered diffraction analysis. The effect of microstructural parameters on the strength-impact toughness combination was investigated. The steel showed an exceptionally low yield ratio, which is beneficial for seismic resistance application. [ABSTRACT FROM AUTHOR]

The present study investigates the influence of Cu 2+ and La 3+ -Cu 2+ doping on the magnetic properties of Sr 1−x La x Fe 12−x Cu x O 19 ( x  = 0.0–0.5) hexaferrite (SrM) compounds. The samples were prepared via facile autocombustion technique followed by sintering. X-ray powder diffraction patterns show the formation of the pure phase of M-type hexaferrite for all x . Invariance in lattice parameters was observed with only Cu 2+ substitution while lattice contraction along c- axis was observed with co-doping La 3+ -Cu 2+ in SrM. The magnetic property of these compounds is explained based on Cu 2+ occupancy in the absence and presence of La 3+ in SrM magnetoplumbite structure. The Cu 2+ doped SrFe 12−x Cu x O 19 sample showed a monotonic decrease in Ms value while La 3+ -Cu 2+ showed a noticeable increase in Ms value with x . Furthermore, while coercivity of Cu 2+ doped SrM reduced with x , the coercivity of La 3+ -Cu 2+ doped SrM showed a marked 12% increase in coercivity at x  = 0.1 (Hc = 4391 Oe) from that of x  = 0.0 (3918 Oe). Interestingly, Cu 2+ doped SrM displayed invariance in Tc ∼ 458.6 °C with x , while La 3+ -Cu 2+ doping reduced Tc by 5% from its x  = 0 (Tc = 451.9 °C) to 429.6 °C. The room temperature Mossbauer spectral analysis confirmed a Cu 2+ preference for the 12 k site and its occupancy is observed to be influenced by the presence of La 3+ ion at the Sr 2+ site. [ABSTRACT FROM AUTHOR]

Isolators are important components of low-noise detector and signal processing systems. Conventional wideband edge-mode isolators offer wide bandwidth, but rarely exceeding two octaves. Using modern computer electromagnetic simulation software, one can optimize the isolator circuit and expand the bandwidth performance. We report on the design, fabrication, and measurement of an edge-mode isolator operating over a multioctave frequency range, from 4 to 22 GHz at 4-K cryogenic temperature. This isolator has good input and output reflection coefficients that are below −15 dB from 4 to 22 GHz. The measured insertion loss is about 0.6 dB from 4 to 17 GHz, rising to 1 dB from 17 to 22 GHz, and the isolation is better than 15 dB from 4 to 13 GHz, degrading to about 10 dB above 13 GHz. This edge-mode isolator with improved bandwidth is suitable for a wide range of low-noise receiver applications. [ABSTRACT FROM PUBLISHER]

The granular ferrite fillers like BaFe12O19 (BaM-P) usually work as an auxiliary material in the EMA composite, but shows weak electromagnetic wave absorbing (EMA) capability (RL > − 10 dB) when single used. In this work, an orderly filled ferrite/polymer composite has been made by a versatile tape casting method. The micron BaFe12O19 template particles (BaM-T) were obtained by a two-step molten salt method and were oriented and uniformly inserted into the BaM-P/polyvinyl butyral (PVB) composite to form a BaM-T/BaM-P/PVB ternary composite with laminated micro-structure. The composite shows greatly enhanced EMA properties with broadening effective EMA bandwidth. The optimal sample displayed a minimum reflection loss of − 45.8 dB at 6.6 GHz and effective EMA bandwidth (RL < − 10 dB) of 3-18 GHz with 2-5 mm thick. The maximum effective EMA bandwidth of 4.16 GHz was obtained at the thickness of 1.8 mm. Finite element simulation verified that, the strong barrier interfaces attributed by the oriented BaM-T flakes can effectively improve absorptive intensity and decrease sample thickness via a particular multiple reflection mechanism. Additionally, the large range of filler particle size from nano to micro can make the effective bandwidth to be broadened. This work demonstrates the great potential of the ferrite materials for EMA application. [ABSTRACT FROM AUTHOR]

Well-defined uniaxial micro-tensile tests are performed on single-crystal ferrite specimens with three different orientations. All specimens reveal a highly reproducible plastic behavior. The {110}<111> and {112}<111> slip systems equally contribute to the deformation, while all other (complex) slip traces can be identified as cross-slip and ‘pencil glide’. No {123}<111> slip system traces were observed. The critical resolved shear stresses of the two active slip systems are close to each other, i.e. CRSS { 110 } = ( 1.0 ± 0.1 ) × CRSS { 112 } . In all the tested specimens, the activation of the primary slip systems (e.g. systems that activate first) follows the Schmid's law. At first glance, the activation of secondary slip systems does not seem to comply with the highest Schmid factor. However, detailed investigation supported by crystal plasticity simulations reveals that the boundary constraints acting on the primary slip direction triggers an increase of the Schmid factors of the activated secondary slip systems, i.e. Schmid's law correctly justified all observed slip traces. Application of the found ferrite slip parameters in crystal plasticity simulations of ferrite-containing steels shows that correct input values are crucial for obtaining meaningful macroscopic predictions. [ABSTRACT FROM AUTHOR]

In this paper, the authors introduce a semianalytical model for the analysis and the design of a permanent magnet (PM) tubular linear generator intended for electrical energy generation from sea waves. The translator of the analyzed machine is constituted by axially magnetized ferrite PMs with alternating polarity and soft magnetic pole pieces in between; a two-pole, double-layer, three-phase winding is located in the slots of the stator. The presented model, based on the use of the Carter coefficient and of the Fourier transform in the direction of the motion, is able to take into account the end effects due to the finite length of the stator. The presence of slots and teeth is subsequently considered by some postprocessing calculation carried on the results of the semianalytical model. Comparison with a finite element analysis and measurements taken on a prototype has been performed to validate the presented model. The model can be easily extended to other translator typologies, e.g., to air core translator with Halbach array of NdFeB PMs. [ABSTRACT FROM AUTHOR]

The one-pot formation of colloidal nanocrystal clusters has recently gained attention because of the new set of phenomena with which such secondary structures are endowed. Nevertheless, given the number of complex processes at play, the correct interpretation of the chemical mechanisms behind the formation of such structures remains a particularly difficult task. In this work, magnetic colloidal nanocrystal clusters with a spinel structure are thoroughly characterized by means of transmission electron microscopy, X-ray diffraction, magnetic measurements, and Raman spectroscopy. The combination of these techniques results in a means of unraveling the structure of the poorly crystalline intermediates and complex products formed throughout the process. Our results suggest that the chemical and crystallographic transformations that the nanostructures undergo at the different stages of the reaction are strongly related to the final morphology of the secondary superstructures obtained, which, in parallel, help to improve the magnetic properties required in their specific final applications. [ABSTRACT FROM AUTHOR]

Oriented growth of patterned cobalt ferrite magnetic thin films on polymeric colloidal crystal films has been carried out employing a room-temperature pulse laser deposition method. The series of colloidal crystal films containing uniform polystyrene particles (180–420 nm) were prepared by self-assembly. Scanning electron microscopy and optical reflectometry were used to confirm the assembly of well-arranged colloidal crystal films. Magnetic films of different thicknesses were deposited. X-ray diffraction measurements confirmed the nano-crystalline structure of cobalt ferrite grown on the spherical-shaped surface. Magneto-optical effects of the patterned thin films were examined and the results illustrated that the increase in film thickness leads to the decrease in coercivity, while the saturation magnetization increases. Furthermore, the magnetic origin of the coercivity variation dependence on the colloidal diameter and film thickness are discussed. Our results suggest that the preparation conditions of the deposited films should be tailored to obtain perpendicular anisotropy in cobalt ferrite films. The adjustable magnetic anisotropy was obtained due to substrate-induced magnetic shape anisotropy. [ABSTRACT FROM AUTHOR]