Magnetic Generation Research Articles

Enhanced strength-plasticity synergy of 304 stainless steel by introducing gradient nanograined single austenite phase structure via USRP and induction annealing

The drawback of low strength of 304 stainless steel could be overcome by fabricating gradient nanostructures (GNS). However, deformation-induced martensite results in magnetic generation and plasticity degradation. In this work, a single austenitic GNS 304 stainless steel is fabricated by first creating a dual-phase GNS through the ultrasonic surface rolling process (USRP), followed by rapid induction heating. The yield strength of the single austenite GNS (520 MPa) is 1.68 times higher than that of the homogeneous coarse-grained structure (310 MP) without sacrificing plasticity (elongation of 65 %). Quantitative calculations indicate that fine grain, dislocation, twinning, and back-stress strengthening contribute to the strength increment by 30 %, 17.5 %, 23.4 %, and 29.1 %, respectively. Coarse-grained regions deform mainly through FCC-HCP-BCC martensitic transformation, whereas the subsurface layer forms stacking faults and twins due to increased stacking fault energy caused by the reduction in grain size. At the topmost layer, the stress required to activate dislocations is lower than that for twinning. Under high-stress conditions, martensite forms along the nanograin boundaries via a phase transition from FCC to BCC. Consequently, the excellent plasticity of the single austenite GNS stems from the synergistic effects of high back-stress hardening, TRIP and TWIP effect.

First-Principles Study of Electronic Structure and Magnetic Properties of SnO2 Co-doped with Transition Metals (Mo, Ru, Rh, and Pd) and Oxygen Vacancies (VO)

The formation energies, electronic structures, and magnetic properties of a series of SnO2 systems co-doped with transition metals (Mo, Ru, Rh, and Pd) and oxygen vacancies (VO) were investigated using plane-wave density functional theory with ultra-soft pseudopotentials. The results show that the formation energy of the Mo-VO-SnO2 system was the smallest among the doped systems, indicating that the system was the easiest to form. The net magnetic moments of the X-VO-doped SnO2 systems (X = Mo, Ru, and Rh) are not zero, indicating that the systems are all in the ferromagnetic state. Among them, the Mo-VO-doped SnO2 system had an enormous net magnetic moment, highest spin polarization rate, and best ferromagnetism, making it an excellent ferromagnetic candidate material. The ferromagnetism of the doping systems originates from the strong hybridization of the 4d orbitals of the unpaired electrons in the dopants. The VO-SnO2 does not exhibit any magnetic properties. Therefore, VO doesn’t play a role in the generation of magnetism

DFT calculations of Cu doped TiO2 ferromagnetic study

There is still some controversy about the room-temperature ferromagnetism generated by transition metal-doped TiO2 and its magnetic generation. In this paper, the samples with different doping ratio were prepared to verify the magnetism of doped TiO2, and then the geometry of copper-doped Ti16O32 supercell system was optimized by using the overall energy density function theory (DFT) and generalized gradient approximation (GGA). The results show that the doped energy band diagram shows electron self-selective cleavage near the Fermi energy level and the addition of Cu atoms does produce ferromagnetism. The magnitude of the induced magnetic moment is related to the distance of Cu atoms and oxygen vacancies. The system with a doped Cu-Cu distance of 3.82 A is more stable, and the ferromagnetism of the doped phase is more stable and lower 29 meV than the antiferromagnetic state in the absence of oxygen vacancies (Cu2Ti14O32), while a magnetic burst occurs in Cu2Ti14O30 after the formation of oxygen vacancies. Magnetic Cu-TiO2 may become a promising adsorbent to be applied in the field of pollutant control.

Performance Analysis and Optimization of Built-In Permanent Magnet and Salient-Pole Electromagnetic Hybrid Excitation Generators for Vehicles

To solve the problems of the low power density of pure electric excitation generator and nonadjustable magnetic field of pure permanent magnet (PM) generator, a salient-pole hybrid excitation generator (HEG) was proposed in this paper. The designed generator realized coexcitation of two magnetic fields by changing the shape of the pole shoes and embedding the combined-pole PM steels. Compared with other HEGs, it had the advantages of high power density, less excitation loss, and small volume. The paper deduced the analytical expressions of the main magnetic field and armature reaction magnetic field of the HEG and analyzed the armature reaction magnetic circuit, the main influencing parameters, and the influence law of each parameter on the generator output performance to complete the parameter matching of the whole machine. The prototype was trial manufactured and tested with the optimized parameters. The results show that the designed HEG has a low voltage regulation rate, good no-load characteristics, and regulation characteristics. It can ensure the regulated output voltage under rated load conditions and meet the application requirement.

Magnetic Generation and Switching of Topological Quantum Phases in a Trivial Semimetal α−EuP3

Topological materials have drawn increasing attention owing to their rich quantum properties, as highlighted by a large intrinsic anomalous Hall effect (AHE) in Weyl and nodal-line semimetals. However, the practical applications for topological electronics have been hampered by the difficulty in the external control of the band topology. Here we demonstrate a magnetic-field-induced switching of band topology in $\alpha{\mathrm{-EuP}}_3$, a magnetic semimetal with a layered crystal structure derived from black phosphorus. When the magnetic field is applied perpendicular to the single mirror plane of the monoclinic structure, a giant AHE signal abruptly emerges at a certain threshold magnetization value, giving rise to a prominently large anomalous Hall angle of $\left|\Theta_{\mathrm{AHE}}\right| \sim 20^{\circ}$. When the magnetic field is applied along the inter-layer direction, which breaks the mirror symmetry, the system shows a pronounced negative longitudinal magnetoresistance. On the basis of electronic structure calculations and symmetry considerations, these anomalous magneto-transport properties can be considered as manifestations of two distinct topological phases: topological nodal-line and Weyl semimetals, respectively. Notably, the nodal-line structure is composed of bands with the same spin character and spans a wide energy range around the Fermi level. These topological phases are stabilized via the exchange coupling between localized Eu-4$f$ moments and mobile carriers conducting through the phosphorus layers. Our findings provide a realistic solution for external manipulation of band topology, enriching the functional aspects of topological materials.

Impact of anti-solar differential rotation in mean-field solar-type dynamos

Context. Over the course of their lifetimes, the rotation of solar-type stars goes through different phases. Once they reach the zero-age main sequence, their global rotation rate decreases during the main sequence until at least the solar age, approximately following the empirical Skumanich’s law and enabling gyrochronology. Older solar-type stars might then reach a point of transition when they stop braking, according to recent results of asteroseismology. Additionally, recent 3D numerical simulations of solar-type stars show that different regimes of differential rotation can be characterized with the Rossby number. In particular, anti-solar differential rotation (fast poles, slow equator) may exist for high Rossby number (slow rotators). If this regime occurs during the main sequence and, in general, for slow rotators, we may consider how magnetic generation through the dynamo process might be impacted. In particular, we consider whether slowly rotating stars are indeed subject to magnetic cycles. Aims. We aim to understand the magnetic field generation of solar-type stars possessing an anti-solar differential rotation and we focus on the possible existence of magnetic cycles in such stars. Methods. We modeled mean-field kinematic dynamos in solar (fast equator, slow poles) and anti-solar (slow equator, fast poles) differential rotation, using the STELEM code. We consider two types of mean field dynamo mechanisms along with the Ω-effect: the standard α-effect distributed at various locations in the convective envelope and the Babcock-Leighton effect. Results. We find that kinematic αΩ dynamos allow for the presence of magnetic cycles and global polarity reversals for both rotation regimes, but only if the α-effect is saddled on the tachocline. If it is distributed in the convection zone, solar-type cases still possess a cycle and anti-solar cases do not. Conversely, we have not found any possibility for sustaining a magnetic cycle with the traditional Babcock-Leighton flux-transport dynamos in the anti-solar differential rotation regime due to flux addition. Graphic interpretations are proposed in order to illustrate these cases. However, we find that hybrid models containing both prescriptions can still sustain local polarity reversals at some latitudes. Conclusions. We conclude that stars in the anti-solar differential rotation regime can sustain magnetic cycles only for very specific dynamo processes. The detection of a magnetic cycle for such a star would therefore be a particularly interesting constraint in working to decipher what type of dynamo is actually at work in solar-type stars.

Stress-Driven Magnetic Barkhausen Noise Generation in FeCo Magnetostrictive Alloy

Stress-driven magnetic Barkhausen noise (MBN) can be potentially used to develop a high-sensitivity dynamic force sensor. MBN is a compositional pulse due to the domain wall movement in ferromagnetic material induced by the external field. In this study, we provide an in-depth understanding of the responsiveness of MBN to external stress using ferromagnetic materials with a high magnetostriction constant ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> ). We demonstrate stress-driven MBN from strong textured Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">29</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">71</sub> alloy wires ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathrm {s}} =117$ </tex-math></inline-formula> ppm)/epoxy resin composite via uniaxial compression testing by changing the stress rate level from 0.55 to 28 GPa/s under a static bias magnetic field of 55 mT. The relationship between the stress rate of the external force and root-mean-square (rms) value of MBN output voltages showed high sensitivity, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {rms}}= 0.00441 (d\sigma /dt)$ </tex-math></inline-formula> , and acceptable linearity that could be used to quantitatively evaluate the dynamic force. This stress-driven MBN generation mechanism could be based on the domain wall movement induced by the inverse magnetostrictive effect of FeCo alloys. We believe that this study will aid in the research focusing on the dynamic magnetostrictive mechanism and development of novel applications for high-sensitivity force sensors that have no batteries.

Design and analysis of tubular permanent magnetic linear generator with 120° phase belt toroidal windings

Purpose To improve the power density and generation efficiency of the tubular permanent magnetic linear generators (TPMLGs) under realistic sea-stator condition, a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) for wave energy conversion is proposed in this paper. Design/methodology/approach First, the structure of the 120°-TPMLG is introduced and its operation principle is analyzed. Second, the design process of the 120°-TPMLG is described. Meanwhile, the finite-element models of the 120°-TPMLG and the TPMLG with traditional fractional pitch windings (T-TPMLG) are established based on the similar overall dimensions. Then, the electromagnetic characteristics of the 120°-TPMLG are analyzed, such as air gap flux density, back electromotive force and load voltage. Finally, a comparative analysis of the magnetic flux density, flux linkage, load and no-load performance of the two generators are conducted. Findings The result shows that the 120°-TPMLG has higher power density and generation efficiency than the T-TPMLG. Originality/value This paper proposes a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) to improve the power density and generation efficiency.

Thermal-magneto-mechanical stability analysis of nanofluid conveying carbon nanotubes based on nonlocal couple stress theory

Carbon nanotubes (CNTs) have extensive biomedical applications in which a heat pulse is applied to the CNTs. The present study encompasses the novelty by focusing on the complicated effect of thermal loads and heat generation on the CNT stability with the aim of preserving and improving the stability. There is also a lack of research that evaluates the size-dependence using appropriate robust non-classic theory, which is incorporated by employing a hybrid method of nonlocal couple stress theory and nonlocal elasticity theory. Additionally, Euler–Bernoulli beam theory is employed for coupling the Navier–Stokes equation of magnetic-fluid flow with the CNT deformation. The CNT stability is evaluated by considering nonlocal and couple-stress sizing effect parameters, Knudsen number, magnetic field intensity, thermal effect, heat generation, and fluid flow velocity. Results indicate that, by rising the temperature gradient and the couple stress sizing effect parameter, the system stability is improved up to 19.07% and 16.58%. Whereas, by increasing the heat generation, the dimensionless critical velocity shows 6.91% decrease, which deteriorates the CNT stability. Results of the present study demonstrates that in CNT applications with the presence of thermal loads, neglect of thermal effects leads to misinterpretation of the system stability.

Finding the Optimal Size of Permanent Magnets for a Transverse Magnetic Flux Generator with a Disk Rotor

Based on the analysis of the transverse flux machine designs, they were found to have a relative design simplicity and a high-power density. The purpose of this work is to determine the optimal height of a permanent magnet and to define its effect on the induced EMF value in the stator coils and the cogging torque, as well as to define the picture of the magnetic flux leakage between the stator poles. To achieve these goals, the 3D model of a low speed generator was studied. The electromagnetic analysis was carried out using a modern software, which allows us to determine the magnetic field distribution in the 3D, as well as the induced EMF value and the rotor cogging torque. The criterion for the optimal calculation is the highest EMF value at the minimum value of the rotor cogging torque. The parameters of the permanent magnets, such as the width and length, remained unchanged, whereas, the height varied from 1 to 8 mm at a 1-mm step. The corresponding dependencies are obtained for each height. The most significant result of the work is the conclusion that the height of the permanent magnet should not exceed the 3-mm value. The significance of the obtained results is that the used methodology allowed finding the optimal height of the permanent magnet, since a further increase in its height leads to no growth in the EMF value, but rather significantly enhances the negative effect from the rotor cogging torque. In addition, the simulation results were supported experimentally.

Universal method for magnetic skyrmion bubble generation by controlling the stripe domain instability

Magnetic skyrmions, which are topological swirling spin textures, have drawn much attention in spintronics because of their use as an information carrier with distinct robustness rooted in their topological nature. Real-time generation of skyrmions is therefore imperative for realizing skyrmion-based spintronic devices. However, to date, experimental demonstration has been limited to exquisite works with well-tuned samples. Here, we report a method to generate skyrmions by driving the stripe instability via an in-plane magnetic field. We have demonstrated that the key parameter determining the stripe domain instability is the stripe width, regardless of other material parameters. This skyrmion generation method can be applicable to generic magnetic films with perpendicular magnetic anisotropy. Our work will facilitate the development of skyrmion-based devices by offering a general method for controlling a large skyrmion population.

Paralleling insulated-gate bipolar transistors in the H-bridge structure to reduce current stress

In this study we present the new power electronic circuit implementation to create the arbitrary near-rectangular electromagnetic pulse. To this end, we develop a parallel- Insulated-gate bipolar transistors (IGBT)-based magnetic pulse generator utilizing the H-bridge architecture. This approach effectively reduces the current stress on the power switches while maintaining a simple structure using a single DC source and energy storage capacitor. Experimental results from the circuit characterization show that the proposed circuit is capable of repeatedly generating near-rectangular magnetic pulses and enables the generation of configurable and stable magnetic pulses without causing excessive device stresses. The introduced device enables the production of near-rectangular pulse trains for modulated magnetic stimuli. The maximum positive pulse width in the proposed neurostimulator is up to 600 µs, which is adjustable by the operator at the step resolution of 10 µs. The maximum transferred energy to the treatment coil was measured to be 100.4 J. The proposed transcranial magnetic stimulator (TMS) device enables more flexible magnetic stimulus shaping by H-bridge architecture and parallel IGBTs, which can effectively mitigate the current stress on power switches for repetitive treatment protocols.

Investigation on magnetic and flow field in magnetorheological jet machining

The instability and spreading out of jet flow outside the focusing tube involved in abrasive waterjet machining can be prevented by using magnetorheological (MR) fluid. The collimated and coherent MR jet in the presence of external axial magnetic field is potential to give a preferable erosion footprint and processing performance. In this research, a magnetic generator was developed and installed on an abrasive waterjet machining system to conduct MR jet erosion experiments on alumina. The induced magnetic field and jet flow field were numerically analyzed to evaluate their effects on material removal. The results indicated that the magnetic flux density increases with an increment of excitation current. The concentration of jet flow can be significantly enhanced by applying external magnetic field, and the velocity attenuation along the flowing direction due to the jet diffusion is restrained. The experimental results indicated that the range of crater is relatively smaller, and the erosion depth is larger when applying magnetic field, which can verify the validity of simulation results.

Investigation on Tripping in Magnetic Generator in Steam-Assisted Gravity Drainage Wells Based on Numerical Simulation

Abstract Magnetic Guidance Technology can meet the precise measurement requirements when drilling steam-assisted gravity drainage (SAGD) oil wells. Magnetic generator is a key part in the Magnetic Guidance Technology. When magnetic generator is tripped into horizontal well, pump pressure and passing capacity of the magnetic source generator in the curved section need to be analyzed. So, a mathematical model of tripping in the magnetic generator is established. If curvature radius, deviation angle, and friction factor are known, the forces acting on the magnetic generator in different positions could be calculated. The finite element (FE) results show that: (1) with depth increasing in the curved section, the equivalent stress on the magnetic generator increases in a fluctuating manner, the contact area, friction drag, and energy loss increase. (2) The greater the hole curvature, the greater tripping in force and the higher pump pressure are needed. The lower friction coefficient is favorable to tripping in the magnetic generator. (3) The friction between the magnetic generator and tubing wall in the horizontal section is much less than that in the curved section. Field applications have shown that the maximum downforce is close to the result of finite element analysis. The research results provide a reasonable reference basis for smooth running of magnetic source generators with different trajectory conditions.

Blink detection and magnetic force generation for correction of lagophthalmos, with specific regard to implant compatibility testing

ABSTRACT Purpose The overall goal was to restore a normal and synchronous blink in unilateral lagophthalmos. We describe the biocompatibility profiling of a novel ferromagnetic implant used for electromagnetic eyelid force generation. Methods A non-contact blink detection system and an electromagnetic stimulation system were designed and tested. A modified Lester-Burch speculum equipped with strain gauge technology was used in blinking force measurement. Samarium–cobalt magnets were prototyped and coated with parylene-C. Biocompatibility testing was performed using NIH/3T3 mouse fibroblast cells with MTT colorimetric assay cytotoxic quantification. Outcome Measures Cellular viability and interleukin concentrations. Results Our system was capable of detecting 95.5 ± 3.6% of blinks in various lighting conditions. Using our force measuring device, the difference between non-paralyzed and paralyzed orbicularis oculi (OO) for normal and forceful blinking closure was 40.4 g and 101.9 g, respectively. A 16.6 × 5.0 × 1.5 mm curved shaped samarium cobalt eyelid implant was successfully developed and showed a reproducible blink at 100 ms with full corneal coverage with external eyelid taping. Compared to gold weights, parylene-C coated samarium cobalt implants showed not only excellent cell viability (82.0 ± 4.9% vs. 88.4 ± 0.9%, respectively, p > .05), but also below detection threshold for pro-inflammatory marker concentrations (interleukin-6 < 2 pg/mL and interleukin-10 < 3 pg/mL). Conclusions We demonstrated excellent in-vitro biocompatibility of our parylene-C coated samarium cobalt implants. We believe that our novel approach can improve the quality-of-life of affected individuals and provides new understanding of blinking biomechanics.

Poly (I:C)- and doxorubicin-loaded magnetic dendrimeric nanoparticles affect the apoptosis-related gene expressions in MCF-7 cells.

Use of nanoparticles as drug carrier vectors has great potential to circumvent the limitations associated with chemotherapy, including drug resistance and destructive side effects. For this purpose, magnetic generation 4 dendrimeric nanoparticles were prepared to carry chemotherapeutic agent doxorubicin (G4-DOX) and immune modulator polyinosinic:polycytidylic acid [Poly(I:C)]. As previously reported, DOX and Poly(I:C) was loaded onto G4 nanoparticles (PIC-G4-DOX). Cellular internalization study using confocal microscopy demonstrated high levels of cellular internalization of PIC-G4-DOX nanoparticles by MCF-7 cells. This resulted in higher efficacy of PIC-G4-DOX nanoparticles in killing MCF-7 breast cancer cells. Alteration in the expression levels of selected genes was determined by RT-qPCR analyses. Proapoptotic NOXA, PUMA, and BAX genes were upregulated, and SURVIVIN, APOLLON, and BCL-2 genes were downregulated, indicating the cell-killing effectiveness of PIC-G4-DOX nanoparticles. Gene expression analysis provided some insights into the possible molecular mechanisms on cytotoxicity of DOX and Poly(I:C) delivered through G4 magnetic nanoparticles. The results demonstrated that PIC-G4-DOX can be useful for targeted delivery affecting apoptotic pathways, resulting in an advanced degree of cancer-cell–killing. They are promising for targeting cancer-cells because of their stability, biocompatibility, higher internalization, and toxicity.

Spin: Ubiquitous, Fundamental, Purposeful: Its Complementary Interactions with Gravity

In a prior article we explained how axial spin of celestial bodies interact with mutual gravitation in the phenomenon of synchronous rotation of our moon and the major moons of the gas giants. We also showed how the same complementary interactions could explain both the nonsynchronous (regular orbits) and the negative rotations in Venus, Uranus and Pluto, as well as in the peripheral small satellites of the gas giants. This paper expands on that theme and identifies the various other areas in which these two fundamental and ubiquitous forces cooperate to bring about many other phenomena in the larger universe. Prominent among these phenomena is the role played by the mother bodies’ axial rotation in determining the direction of the orbital motion of their satellite bodies. The other effects include the appearance and maintenance of the spherical shape of large celestial bodies, generation of magnetism in planets, their respective roles in the formation of solar nebulae and proto-planetary disks, and the flattened profile of spiral and elliptical galaxies. Another important finding reported in this paper is the close relationship that exists between the size of planets, as well as the stars, with their axial rotation speeds. This increase of axial rotation speed of celestial bodies in direct proportion to the mass of those bodies, we believe serves to counteract the inward thrust of gravity, in exact proportions and thus help maintain the roughly spherical contour of those bodies. This finding even extends to spiral galaxies, where the axial rotation speed seems to be positively related to the size of the galaxy. This phenomenon and others suggest that spin is a fundamental and purposeful property of matter. Thus, in this paper we stress the important contributions made by the collaborative interactions between the ubiquitous gravity and spin in matter at the level of the fundamental particles, as well as in large celestial bodies, including the largest units in the universe, the galaxies.

Rotor loss optimization and comprehensive analysis of high-speed magnetic levitation turbine generator

Rotor loss optimization and comprehensive analysis of high-speed magnetic levitation turbine generator

Nucleation of Magnetic Micro-Inhomogeneities by an Electric Field

The electric field-induced magnetic inhomogeneities generation is demonstrated in (BiLu)3(FeGa)5O12 iron garnet film grown on (110) Gd3Ga5O12 substrate. The typical shapes of the generated structures are presented.

Design and Prototype Test Data for a 300 kW Active Magnetic Bearings-Supported Turbine Generator for Natural Gas Pressure Letdown

Abstract A 300 kW integrated and fully sealed turboexpander-generator for natural gas pressure letdown (PLD) was developed by Baker Hughes, a GE company (BHGE), in conjunction with Calnetix Technologies. This paper describes the design and analysis of the generator, magnetic bearings, and touchdown bearings, with a focus on the dynamic performance and key characteristics of the machine. The permanent magnet (PM) synchronous generator is supported by PM-biased, homopolar magnetic bearings and has a maximum continuous operating speed (MCOS) of 31.5 krpm. A touchdown bearing system is implemented using rolling element bearings with soft mount supports. Also described is a thrust load balancing scheme that uses the thrust bearing coil current for reference. A time transient simulation showing the effect of process conditions on the AMB dynamics is shown. Preliminary data from the prototype mechanical run test are shown, including transfer functions measured using the magnetic bearings, Campbell diagram, and touchdown bearing drop test results.