Strong Magnetic Strength Research Articles

Novel Design of 3-D Microstructure Contact Material Generating Autoexcitation Magnetic Field

The development of vacuum circuit breaker (VCB) toward large current and high voltage is extremely limited with contact material. Herein, a new type of VCB contact model including microstructure is proposed. Emerging contact material achieves the breakthrough from external applying to self-excited magnetic field, besides strong magnetic strength and low temperature rise. Three-dimensional finite-element simulations, which contain microcoil, unit groups, and coupled contacts, were implemented. And the influence factors involve eddy current losses, iron core diameter, units’ spacing, and copper–chromium layer thickness. Simulation results indicate that the magnetic field is the most efficient when the distance between the coupled coils is 1.65 mm and the thickness of the Cu–Cr layer is 3 mm. Moreover, the relative practical models and measures were carried out to verify the distribution of magnetic field, and the results were in good agreement with theoretical predictions. Therefore, the theoretical data can guide the design of practical contact models and support the optimization of structural parameters, applied to vacuum interrupter.

Ultrafast High-Energy Electron Radiography Application in Magnetic Field Delicate Structure Measurement

Transient electromagnetic field plays very important roles in the evolution of high-energy-density matter or laser plasma. Now, a new design is proposed in this paper to diagnose the transient magnetic field, using relativistic electron bunch as a probe based on high-energy electron radiography. And based on this scheme, the continuous distribution of magnetic strength field can be snapshotted. For 1 mm thick quadrupole magnet model measured by 50 MeV probe electron beams, the simulation result indicates that this diagnosis has spatial resolution better than 4 microns and high measurement accuracy for strong magnetic strength and high magnetic gradient field no matter whether the magnetic interaction is focusing or defocusing for the range from -510 T∗μm to 510 T∗μm.

MRI-Compatible Injection System for Magnetic Microparticle Embolization.

Dipole field navigation and magnetic resonance navigation exploit B0 magnetic fields and imaging gradients for targeted intra-arterial therapies by using magnetic drug-eluting beads (MDEBs). The strong magnetic strength (1.5 or 3 T) of clinical magnetic resonance imaging (MRI) scanners is the main challenge preventing the formation and controlled injection of specific-sized particle aggregates. Here, an MRI-compatible injector is proposed to solve the above problem. The injector consists of two peristaltic pumps, an optical counter, and a magnetic trap. The magnetic property of microparticles, the magnetic compatibility of different parts within the injector, and the field distribution of the MRI system were studied to determine the optimal design and setup of the injector. The performance was investigated through 30.4-emu/g biocompatible magnetic microparticles (230 ± 35 μm in diameter) corresponding to the specifications needed for trans-arterial chemoembolization in human adults. The system can form aggregates containing 20 to 60 microparticles with a precision of six particles. The corresponding aggregate lengths range from 1.6 to 3.2 mm. Based on the injections of 50 MRI-visible boluses into a phantom which mimics realistic physiological conditions, 82% of the aggregates successfully reached subbranches. This system has the capability to operate within the strong magnetic field of a clinical 3-T MRI, to form proper particle aggregates and to automatically inject these aggregates into the MRI bore. Moreover, the versatility of the proposed injector renders it suitable for selective injections of MDEBs during MR-guided embolization procedures.

Enhanced synergetic effect of Cr(VI) ion removal and anionic dye degradation with superparamagnetic cobalt ferrite meso\u2013macroporous nanospheres

The overall effectiveness of a photocatalytic water treatment method strongly depends on various physicochemical factors. Superparamagnetic photocatalysts have incomparable advantage of easy separation using external magnetic fields. So, the synthesis of efficient superparamagnetic photocatalysts and the development of a deep understanding of the factors influencing their catalytic performances are important. CoxZn1−xFe2O4 (x = 0, 0.5, 1) ferrite nanospheres were synthesized by the solvothermal route. The reduction of Cr(VI) and degradation of methyl orange (MO) impurities were carried out in single- and binary-component system under visible light irradiation. The adsorption experiments were done by the catalyst in the water solution containing the impurities. The magnetic and optical properties were studied by VSM and UV–Vis analysis. The nature of porosity was investigated using the BET method. 3D nanospheres of diameter about 5–10 nm were fabricated. The binary-contaminant system exhibited synergetic photocatalytic effect (80% improvement in activity rate) against the nanoparticles. The corresponding mechanism is discussed. CoFe2O4 exhibited better adsorption, photocatalytic and magnetic separation efficiency due to its higher surface area (50% higher), narrower band gap (25% lesser), smaller crystallite size, a strong magnetic strength (51.35 emu/g) and meso–macro hierarchical porous structure. The adsorption of Cr(VI) and MO can be approximated to the Langmuir and Freundlich model, respectively.

One-way translational magnetic mass damper model for structural response control against dynamic loadings

Structural responses should be reduced to minimize the consequent structural damage caused by dynamic excitation. The one-way translational magnetic mass damper model is developed as a new type of damper for the purpose of structural response control. The damper utilizes the concept of repulsive force between magnets with same poles to create a magnetic force to stabilize or bring the structure back to its original position. The dynamic performance of the structure was tested using a harmonic shaking table. In this study, the three parameters used are excitation speeds: 2.5V (low), 6.0V (medium) and 8.5V (high); strength of magnets: weak (N35), medium (N45) and strong (N52); and the mass in the damper: 40 g, 101 g and 162 g. The correlations of the parameters towards the structural displacement are verified in the testing. The displacement is highly reduced up to 100% at the first level and 85.2% at the fifth level. The most optimum structural response control was attained when a strong magnetic strength and mass of 162 g are used. When tested with three excitation speeds; 2.5V, 6.0V and 8.5V, the damper with this setting provides the optimum damping effect towards the structure in terms of displacement.

Synthesis of magnetic nanoporous carbon from metal-organic framework for the fast removal of organic dye from aqueous solution

In this paper, a magnetic nanoporous carbon (Fe3O4/NPC) was successfully synthesized by using MOF-5 as carbon precursor and Fe salt as magnetic precursor. The texture properties of the as-synthesized nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), and N2 adsorption–desorption isotherms. The Fe3O4/NPC had a high surface area with strong magnetic strength. Its adsorption behavior was tested by its adsorption capacity for the removal of methylene blue from aqueous solution. The results demonstrated that the Fe3O4/NPC had a high adsorption capacity, rapid adsorption rate, and easy magnetic separabilty. Moreover, the adsorbent could be easily regenerated by washing it with ethanol. The Fe3O4/NPC can be used as a good alternative for the effective removal of organic dyes from wastewater.

Faraday rotation and polarization-modulated intense femtosecond laser pulses in a field-ionizing gaseous medium

In this paper we investigate the propagation of an intense linearly polarized laser through an ionizing gaseous medium in the presence of an axial strong magnetic field, addressing the modulation of laser polarization. Our simulation indicates that the laser polarization can be dramatically modulated and shows complicated temporal patterns (Lissajous curves). This striking phenomenon can be attributed to the collective movement of ionized electrons, in contrast to the traditional Faraday rotation in which the rotation angle of the laser polarization derived from the linear response of the medium is time independent. We take the weighted average of the rotation angle over the whole pulse duration and find that it explicitly relies on strong magnetic strength as well as the incident laser intensity. Our finding has implications in strong magnetic diagnosis, laser intensity calibration, and the generation of polarization-modulated light sources.

Magnetic solid base catalyst CaO/CoFe2O4 for biodiesel production: Influence of basicity and wettability of the catalyst in catalytic performance

A novel magnetic solid base catalyst CaO/CoFe2O4 was successfully prepared with CoFe2O4 synthesized by hydrothermal method as the magnetic core and applied to the transesterification of soybean oil for the production of biodiesel. The magnetic solid base catalysts were characterized by a series of techniques including CO2-TPD, powder XRD, TGA, TEM and the contact angle measurement of the water droplet. It was demonstrated that CaO/CoFe2O4 has stronger magnetic strength indicating perfect utility for repeated use and better basic strength. Compared with CaO/ZnFe2O4 and CaO/MnFe2O4, solid base catalyst CaO/CoFe2O4 has better catalytic performance, weaker hydroscopicity and stronger wettability, demonstrating that catalytic performance was relative to both basicity of catalyst and the full contact between the catalyst and the reactants, but the latter was a main factor in the catalytic system.

A facile co-gelation route to synthesize FeCo/carbon nanocomposites and their application as magnetically separable adsorber

A new kind of magnetic porous FeCo/carbon nanocomposites was successfully synthesized by using a facile co-gelation sol–gel route. The sol–gel process of this route started from an ethanol solution containing teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates. With the evaporation of solvent, the weak acidity produced from hydrolysis of metal nitrates simultaneously catalyzed the polymerization of FA and the hydrolysis of TEOS, which led to the inorganic/organic hybrid xerogel, accompanying metal salts spontaneously captured in the xerogel. The composites obtained have high surface areas, pore volumes and strong magnetic strengths, which make them exhibit excellent performance of adsorption for bulk dyes and easily separated from solution by external field after adsorption. Compared to the previous methods, this route is very simple and operable for the preparation of magnetic porous carbon composites. Such facile co-gelation route also provides a common path to the synthesis of nanoscale metal or alloy embedded in the porous carbon materials.

Numerical simulations of interfacial instabilities on a rotating miscible magnetic droplet with effects of Korteweg stresses

Interfacial instability of a miscible magnetic droplet in a rotating Hele-Shaw cell is simulated numerically. The influence of magnetic strengths, the Korteweg stresses, and their coupled effects are first discussed qualitatively by fingering patterns and streamlines. Quantitative measurements are evaluated by interfacial length L, number of fingers n, and diameter of gyration Dg. The results confirm with coupling rotational effects more vigorous fingering instability occurs on stronger magnetic strengths and less effective surface tensions (Korteweg stresses). Without the effects of Korteweg stresses, significant nonlinear fingering merges occur which lead to reduction in fingering number, early decay of interfacial length and reversed plane trajectories. Before the occurrence of fingering merges, monotonic growths of interfacial lengths, constant fingering numbers, and nearly linear pattern trajectories are observed. If the significant Korteweg stresses are taken into account, the nonlinear merge is prevented and the features of fingering patterns resemble the immiscible situations remarkably. The fingering behavior can be approximated by a master line of dL∕dDg≈0.386n+0.13 within the linear fingering region.

Motion of miscible magnetic fluids in a dynamic magnetic field

Displacements of a miscible magnetic layer in a capillary tube under a moving ring‐shaped magnet are studied numerically. The magnet is adjusted dynamically to maintain a constant distance from the front mixing interface on the centerline. Control parameters, such as magnetic strength, effective viscosity variation due to magnetization, diffusion and the position of the magnet, are analyzed systematically. Motion of the magnetic layer is evaluated by two quantitative measurements, i.e. movement of center of gravity and spread of layer width. In general, the moving speed of the center of gravity depends only slightly on the magnetic strength, and is found slower at a higher viscosity ratio and a closer placement to the front interface as well if the magnet is placed amid the layer. A weaker spread occurs in situations of stronger magnetic strength, lower viscosity parameters and also placements near the rear interface. A multi‐front finger results if the magnet is positioned ahead of the front interface.

An evolutionary feature of the magnetic field related to flares in active regions

An evolutionary feature of the magnetic field related to flares in active regions - Incorporation of the Magnetic Flux of the Same Polarity (IMFSP) was studied in this paper. The statistics show that IMFSP related to a major X-ray flare (I ≥M) needs to have a stronger magnetic strength and gradient: (1) Two or more magnetic fluxes of the same polarity located near a magnetic area of the opposite polarity split or push away the flux of the opposite polarity and merge together. The maximum magnetic strength among them is not less than 320 G, and the minimum magnetic strength is not less than 80 G. (2) The new polarity inversion line is formed after the merger. The maximum gradient of the longitudinal field near the new polarity inversion line is not less than 0.12 G km−1. The statistics also show that IMFSP is a rare phenomenon, 92% of them are accompanied by major X-flares. IMFSP is likely induced by two effects at least: (1) the horizontal motion of the matter beneath the photospheric surface moves the magnetic flux; (2) the magnetic flux emerges and grows continuously. The physical reasons that IMFSP results in the flare are discussed.