Good Magnetic Performance Research Articles

Beam loss reduction by magnetic shielding using beam pipes and bellows of soft magnetic materials

One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. A Ni–Fe alloy (permalloy) was selected for the material of the pipe parts and outer bellows parts, while a ferritic stainless steel was selected for the flanges. An austenitic stainless steel, which is non-magnetic material, was used for the inner bellows for vacuum tightness. To achieve good magnetic shielding and vacuum performances, a heat treatment under high vacuum was applied during the manufacturing process of the vacuum chambers. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3GeV rapid cycling synchrotron beam line, the closed orbit distortion (COD) was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.

Preparation and Adsorption Property of Glutathione Magnetic Molecularly Imprinted Polymers

The aim of this work was to produce a kind of magnetic molecular imprinted polymers (MMIPs) with core-shell structure and good magnetic separation performance. Compared with the preparation of traditional MIPs, a novel process was adopted to prepare MMIPs with good simplicity, flexibility and selectivity, in which Fe3O4 NPs were firstly prepared by a reverse microemulsion method, and subsequently directly added to the mixed solution to undergo the polymerization reaction without washing and drying. This method avoids availably the agglomeration and oxidation of Fe3O4 NPs. The MMIPs for glutathione (GSH) specific recognition (GSH-MMIPs), with core-shell structure, were prepared via one-step method polymerization, in which GSH as template molecule, N-vinylpyrrolidone (NVP) and acrylamide (AM) as functional monomers, N,N'-methylene bisacrylamide as crosslinker, H2O2-Vc as initiator and Fe3O4 nanoparticles (NPs) modified with γ-methacryloxypropyltrimethoxysilane (KH-570) as magnetic carrier. The as-prepared polymers were characterized by using of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). The results demonstrated that an imprinted polymer layer was successfully coated onto the surface of modified Fe3O4 NPs, resulting in a narrow diameter distribution and good magnetic responsibility. The specific adsorption equilibrium and selectivity were evaluated by batch rebinding studies. The Scatchard analysis showed that there were two kinds of binding sites in the GSH-MMIPs, the dissociation constants were 8.786×10 mol/L and 5.424×10 mol/L, and the corresponding maximum adsorption capacities of GSH onto GSH-MMIPs were 49.195 mg/g and 155.003 mg/g, respectively. The selectivity of the GSH-MMIPs was also evaluated to determine the rebinding capability of GSH and its analogues, compared with that of the magnetic non imprinted polymers (MNIPs) with similar chemical components. The GSH-MMIPs with high imprinting factor of 3.99 indicated that it was of good selectivity. This protocol was further employed for the extraction and separation of GSH from an aqueous solution.

Facile synthesis of magnetic hierarchical MgO–MgFe2O4 composites and their adsorption performance towards Congo red

MgO–MgFe2O4 composites have been synthesized by a facile method, and they showed enhanced adsorption capacity and good magnetic separation performance.

Synthesis of Fe3O4 Nanotubes under Assistance of Microwave by Tuning Chemical Deposition Mechanism and its Magnetic Properties

To overcome the overcoming of agglomeration and reclamation of nanoparticulate materials, it is imperative to synthesize nanosized materials with other morphologies. Fe3O4nanotubes were synthesized by using anodized aluminum oxide as template under microwave assistance by tuning the deposition mechanism in this work. The obtained nanotubes were characterized by the means of XRD and SEM. Its magnetic property was also investigated. Results show that tubes are of the spinel structure, a layer of about 30 nm Fe3O4was deposited attaching to the AAO wall, and the nanotubes possess good magnetic performance.

ChemInform Abstract: Microwave Magnetic Properties of Soft Magnetic Thin Films

AbstractReview: 35 refs.

Vacuum chamber made of soft magnetic material with high permeability

In particle accelerators, a very effective way to shield an external magnetic field, which affects the beam inside the vacuum chambers, is to manufacture the vacuum chambers using soft magnetic materials with high permeability. We selected a permalloy and a ferritic stainless steel as candidates of those magnetic materials. However, until now the vacuum performance of vacuum chambers made of magnetic material does not yet have a proven track record.Therefore we made a list of items to be examined and verified. These items are listed as follows.1.General vacuum performance of the magnetic materials.2.Magnetic annealing condition and its effect on each performance.3.Magnetic and vacuum characteristic of a vacuum chamber made of soft magnetic material.The outgassing rate of the magnetic materials was equivalent to that of an austenitic stainless steel. A good magnetic shielding performance is obtained by annealing at higher temperatures than 850°C for both magnetic materials, although the performance declines, if the annealing temperature is too high. Furthermore the magnetic annealing in good vacuum is combined with vacuum heat treatment. The TDS spectrum showed that the reduction of hydrogen outflux from the bulk material near the surface was achieved by this process. Finally, we successfully produced a vacuum chamber with such a magnetic material, which will be used in a beam line at the 3GeV J-PARC synchrotron, because satisfying magnetic shielding and vacuum performance were obtained.

Magnetic performance and corrosion resistance of electroless plating CoWP film

The CoWP film with good magnetic performance and corrosion resistance was electrolessly plated from alkaline solution. The technical parameters of the electroless plating system were optimized. When the pH value of electroless plating solution was 11.0 and the reducing agent (NaH2PO2) content was 0.4 mol·L−1, the target chemical reactions proceeded in the electroless plating solution smoothly with negligible interference and side effects. CoWP film prepared under optimal deposition condition contained more hexagonal close-packed (hcp) cobalt (ɛ-Co) of [110] and crystallographic orientation of Co [002]. VSM analysis reveals that the saturation magnetization of the CoWP film is 100∼220 Am2·kg−1 and coercivity is (2.87∼4.38)×104 A·cm−1. The corrosion behavior of CoWP film in 3.5% NaCl aqueous solution was studied by electrochemical experiments. The results prove that the corrosion resistance of the CoWP film deposited under the optimal deposition condition exhibites relatively lower corrosion current of (3.054∼3.162)×10−6 A·cm−2. The surface morphology analysis indicates that the film is smooth and composed of regular-shaped crystallites.

Magnetic properties and thermal stability of (Fe,Co)-Mo-B-P-Si metallic glasses

A series of ferromagnetic metallic glasses with compositions (Fe,Co)78Mo1(B,P,Si)21 are shown to possess good thermal stability and soft magnetic performance. The thermal stability inside the supercooled liquid temperature region was evaluated using Kissinger analysis of primary crystallization, time-temperature-transformation (TTT) diagrams, and the extent of the supercooled liquid region (ΔTx). The phosphorus-free alloy, Fe78Mo1B15Si6, had an activation energy (Ea) of 414 kJ/mol, ΔTx ∼ 50 K, and began devitrifying after about 1 min at 730 K. By way of comparison, the phosphorus-containing alloy, Fe78Mo1B13P6Si2, had an Ea of 440 kJ/mol, ΔTx ∼ 45 K, and began devitrification after 10 min at 730 K. High saturation magnetization (μ0Ms ∼ 1.45-1.55 T) and low coercivity (Hc ∼ 20 A/m) are demonstrated across the composition range. Core loss measurements of toroidal cores are shown to be less than 12 W/cm3 at 1 T, maximum induction amplitude (under both sinusoidal and square waveforms). Trends were established for magnetic and thermal stability as a function of metalloid and magnetic transition metal composition.

Microwave magnetic properties of soft magnetic thin films

We review our works that focus on the microwave magnetic properties of metallic, ferrite and granular thin films. Soft magnetic material with large permeability and low energy loss in the GHz range is a challenge for the inforcom technologies. GHz magnetic properties of the soft magnetic thin films with in-plane anisotropy were investigated. It is found that several hundreds of permeability at the GHz frequency was achieved for Co100−xZrx and Co90Nb10 metallic thin films because of their high saturation magnetization, and an adjustable resonance frequency from 1.3 to 4.9 GHz was obtained. Compared with the metallic thin films, the weaker saturation magnetization of Ni-Zn ferrite thin films results in several tens of permeability at the GHz frequency, but the larger resistivity of the ferrite prepared in situ without any heating treatments has lower energy loss. In order to obtain materials with large permeability and low energy loss in the GHz range, the [CoFe-NiZn ferrite] composite granular thin films were investigated, where the advantage of higher saturation magnetization for the metallic alloy and the high resistivity as well as high saturation magnetization for the ferrite results in a good GHz magnetic performance.

Electrodeposition of Fe-Ni-S Soft Magnetic Film

Fe-Ni-S alloy film was prepared on red copper foil by electrodeposition from a acidic bath containing boric acid as a buffer agent and sodium citrate as a complexing agent.The effects of the bath composition,and the deposition parameters on the surface morphology and the composition of the alloy coating were studied by SEM and EDS.As a result,a smooth coating with no crack and little stress was obtained from the plating bath by adding 2 g/L saccharin and 0.4 g/L 1,4-butynediol.The cathodic current density and the plating bath pH have little effect on the coating composition,but the temperature has great effect.Fe73Ni9.5S17.5 film was prepared in optimized plating conditions,and XRD analysis showed that the coating structure is amorphous.The film has good soft magnetic performances with higher saturation magnetization(Ms≈876.25 kA/m) and lower coercivity(Hc≈4.96 kA/m) at room temperature.Cyclic voltammetry and the cathodic polarization curves indicated that thiourea can promote the co-deposition of Fe-Ni-S alloy.

Synthesis and Characterization of Superparamagnetic Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub> Core-Shell Composite Nanoparticles

The Fe3O4@SiO2 composite nanoparticles were obtained from as-synthesized magnetite (Fe3O4) nanoparticles through the modified Stöber method. Then, the Fe3O4 nanoparticles and Fe3O4@SiO2 composite nanoparticles were characterized by means of X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). Recently, the studies focus on how to improve the dispersion of composite particle and achieve good magnetic performance. Hence effects of the volume ratio of tetraethyl orthosilicate (TEOS) and magnetite colloid on the structural, morphological and magnetic properties of the composite nanoparticles were systematically investi-gated. The results revealed that the Fe3O4@SiO2 had better thermal stability and dispersion than the magnetite nanoparticles. Furthermore, the particle size and magnetic property of the Fe3O4@SiO2 composite nanoparticles can be adjusted by changing the volume ratio of TEOS and magnetite colloid.

Synthesis and microwave absorbing properties of FeCo alloy particles/graphite nanoflake composites

Exfoliated graphite was processed into nano-sized flakes by jet milling, ultrasonication and acid treatments, and then FeCo alloy particles were uniformly deposited onto the surface of the prepared graphite nanoflakes (GNFs) by a co-deposition and subsequent annealing process in reducing atmosphere. The FeCo-GNFs composites demonstrate good soft magnetic performance and effective microwave absorption, especially in the lower frequency range. The strongest absorption reaches −30.6 dB at 7.4 GHz with a coating thickness of 2 mm. Furthermore, effective microwave absorption at different frequency bands can be acquired by adjusting the coating thicknesses and filling ratios of FeCo-GNFs absorber. Considering the low cost and high efficiency, the FeCo-GNFs composites have great potential as microwave absorber for practical applications.

Synthesis and Microwave Absorbing Properties of FeCoNi Alloy Particles/Graphite Flaky Composites

Exfoliated graphite was separated into nano-sized flakes by ultrasonication and acid treatment,and then FeCoNi alloy particles were deposited uniformly on the surface of flakes by co-deposition method and annealing treatment process.Magnetic and microwave Absorbing properties of the obtained samples were measured.The results show that the synthesized composites possess good soft magnetic performance and effective microwave Absorption.The composite consisting of Fe3Co6Ni/graphite flakes annealed at 600℃ as an Absorber has the maximum Absorption value of-24dB at 12.6GHz,and the effective Absorbing bandwidth(-5dB) is about 8GHz.The characteristics of microwave Absorption can be controlled by adjusting element ratios in alloy and the parameters of heat treatment process.This kind of composite has great potential and investigation value in microwave Absorbing fields.

High-coercivity SmCo5 thin films deposited on glass substrates

Structural and magnetic properties of SmCo5 thin films grown on glass substrates with a Cr underlayer were investigated. The nanocrystalline SmCo5 film with a (112¯0) texture exhibited high in-plane intrinsic coercivity up to 26.5 kOe and a large in-plane magnetic anisotropy. The crystallinity of the SmCo5 layer plays an important role, which is strongly dependent on the texture and the morphology of the Cr underlayer. A smooth Cr underlayer with a (200) texture and a good crystallinity is desired for the SmCo5 film with a good magnetic performance. This work demonstrates a process to achieve high intrinsic coercivity and large in-plane magnetic anisotropy SmCo5 films on glass substrates deposited at a relatively low temperature (400 °C).

Magnetically Levitated Rotary Artificial Heart Pump with Axially Suspended Motor

The lifetime of a rotary blood pump as an artificial heart is mainly determined by the durability of mechanical parts such as bearings and seals. The purpose of this study is to develop a durable centrifugal blood pump with self-bearing motor techniques. A magnetically suspended centrifugal blood pump by using an axially levitated motor is reported. The axially levitated motor consists of a top stator, a levitated rotor, a bottom stator, and a permanent magnet bearing. The levitated rotor is set between the top and the bottom stator. The axial position of the rotor is controlled by using the electromagnets. The maximum head pressure and the maximum flow rate of the magnetically suspended centrifugal pump were 200 mmHg and 8 1/min, respectively. The developed pump displayed good magnetic suspension performance and sufficient pump performance as a ventricular assist device.

Bi/sub 3/Fe/sub 5/O/sub 12/ thin film visualizer

Micrometer thick Bi/sub 3/Fe/sub 5/O/sub 12/ (BIG)[001] films were grown onto Gd/sub 3/(ScGa)/sub 5/O/sub 12/[001] single crystals by the pulsed laser deposition technique. The films are of epitaxial quality with a lattice constant of 1.263 nm. Narrow x-ray rocking curves (full width at half maximum: 0.06 deg) and narrow ferromagnetic resonance lines (widths of 25 Oe) indicate good crystalline quality and magnetic performance. The films possess in-plane magnetization, Faraday rotation as high as -7.8 deg//spl mu/m at 630 nm wavelength, and the magnetization M-H curves are linear in the field range from -1.6 kOe to +1.6 kOe. The magneto-optical (MO) properties are almost temperature independent between 5 K and 200 K. This enables the use of thin BIG films as visualizers of magnetic fluxes in high-T/sub c/ superconductors. Magnetic fluxes have been visualized in YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) ceramics with an artificial grain boundary. The sensitivity expressed as Faraday rotation angle (per film thickness) per magnetic field unit was found to be 4.9 deg/(kOe./spl mu/m) in a 730 nm thick BIG film.

Mixture Homogeneity and its Influence on the Sintering and Magnetic Performance of MnZn-Ferrites

The homogeneity of the green mixture, during the manufacturing of MnZn-Ferrites, is a process parameter which can be measured in a quantitative way. This parameter, depends on the morphological properties of the raw materials and determines the final power losses of the sintered products. By influencing this parameter with appropriate techniques good magnetic performances can also be achieved without the usage of extra sintering dopants.

Correlation between grain orientations and domain structure in industrial grain-oriented SiFe sheets (Hi-B)

We have studied the correlation between grain misorientations and static and dynamic domain structures in grain-oriented 3% SiFe industrial sheets (Hi-B). We discuss the values of the misorientation angles and the coating stress one giving good magnetic performances.