• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.250-255
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• 2000

Double rectangular spiral thin-film inductors were fabricated using $Fe_{86.7}Zr_{3.3}B_{4}Ag_{6}$ thin film with high permeability and resistance, in which easy axis of magnetization of the thin-film was perpendicular or parallel to the current direction. The perpendicular geometry inductor revealed higher inductance than the parallel geometry one, because spin aligns of magnetic film were more easily along the field direction due to higher field intensity in the perpendicular geometry. The increase of the inductance, however, resulted in the decrease of resonance frequency. The permeability was monitored by annealing the thin-films at different temperatures. With increasing the permeability, the inductance increased, but total resistance also increased due to the increase in magnetic core loss. As the resonance frequency was higher in air-core inductor than in magnetic thin-film core inductor, it is suggested to increase the resonance frequency that the characteristic of air-core inductor rather than the magnetic properties of the thin-film should be enhanced..

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.191-195
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• 2000

With the object of developing a non-gap choke core, effects of annealing in oxygen atmosphere on magnetic properties for Fe$_{78}$Si$_{9}$B$_{13}$ amorphous alloy were investigated. After annealing for 2 hrs at 440 $^{\circ}C$, optimum magnetic properties for choke core were obtained, where the effective permeability was 180 and was almost constant up to several MHz, and the decrease in permeability upon large DC bias current of 12 A or DC bias magnetic field of 8,000 A/m was very little. Moreover the AC magnetic loss was very low as compared to the conventional choke cores. Upon the optimum annealing, the magnetic hysteresis loop was inclined accompanying the increase of coercive force and the appearance of fine crystallites of $\alpha$-Fe phase. The good choke core properties was considered to be due to the suppression of domain boundary motion and domain refinement by the crystallites.

• Journal of the Korean Magnetics Society
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• v.17 no.6
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• pp.226-231
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• 2007

High frequency loss property of nanocrystalline amorphous ribbon with a high resistivity insulation layer of $TiO_2$ and $SiO_2$ was studied. The insulation layer was fabricated by sol-gel method using dip-coating. The optimum composition ratio of metal alkoxide and slurry for fabrication of insulation layer was established and insulation layer with high adhesion was coated on the nanocrystalline amorphous ribbon. Frequency loss of magnetic core material manufactured on nanocrystalline amorphous ribbon with the surface insulation layer decreased over 40 % compared with that of magnetic core material without surface insulation layer. The insertion loss of an inductive coupler, which was prepared by using magnetic core material coated insulation layer, decreased due to reduction of frequency loss for magnetic core material and insertion loss decreased in proportion to frequency.

• Nano
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• v.13 no.11
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• pp.1850128.1-1850128.10
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• 2018

Glutathione (GSH), the protective agent and reducing agent, has been widely used to prepare gold nanoclusters (GSH-Au NCs) with stable fluorescence properties and negative charge of the surface. Meanwhile, polyethyleneimine (PEI) was used as the modification agent to synthesize magnetic ferroferric oxide nanoparticles ($Fe_3O_4$) with fantastic dispersibility and positive charge of the surface. Based on the electrostatic adsorption force, magnetic nano-$Fe_3O_4@GSH-Au$ NCs core-shell microspheres composed of magnetic $Fe_3O_4$ nanoparticles modified by PEI as the core and GSH-Au NCs as the shell were assembled. The prepared $Fe_3O_4@GSH-Au$ NCs microspheres harbored a uniform size (88.6 nm), high magnetization (29.2 emu/g) and excellent fluorescence. Due to the coordination bond action between Au atom and sulfhydryl (-SH), amino ($-NH_2$), carboxyl (-COOH) in sweat, $Fe_3O_4@GSH-Au$ NCs could combine with latent fingerprints. In addition, $Fe_3O_4@GSH-Au$ NCs with good fluorescence and magnetism could detect fingerprints on various objects. Significantly, the powders were not easy to suspend in the air, which avoided the damage to the health of forensic experts and the fingerprints by only powder contacting. Above all, $Fe_3O_4@GSH-Au$ NCs was successfully applied to the latent fingerprint visualization, which has great potential in forensic science.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.40-44
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• 2001

Recently. the high-tc superconducting fault col-rent limiters (SFCL) are studied worldwide to be classified as a resistive type or an inductive type such as a magnetic shielding type and a inductive type. The high-tc SFCL wish an open core belongs to the magnetic shielding type SFCL. Unlike conventional magnetic shielding type SFCLS it uses the open core to reduce the mechanical vibrations and installation space, The high-tc SFCL with an open core was designed and manufactured by stacking three BSCCO 2212 tubes. It was tested in the maximum source voltage of 400 Vrms. The results such as the reduction of fault current and impedance of the SFCL are described in this paper. The results show that the fault current in the source voltage of 400 Vrms was reduced to be about 123 Apeak. about 3.9 times greater than the normal state current. Also, the impedance of the high-tc SFCL was about 9${\Omega}$ about 9 times greater than the normal state impedance. The impedance of the SFCL appears just after the fault, and its size is dependent on the source voltage. From the impedance, the inductance of the SFCL was calculated.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2279-2282
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• 2007

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical α-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 °C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 °C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

• Journal of Magnetics
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• v.16 no.3
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• pp.318-321
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• 2011

A new Fe-based amorphous compound powder was prepared from Fe-Si-B amorphous powder by crushing amorphous ribbons as the first magnetic component and Fe-Cr-Mo metallic glassy powder by water atomization as the second magnetic component. Subsequently by adding organic and inorganic binders to the compound powder and cold pressing, the new Fe-based amorphous compound powder cores were fabricated. This new Fe-based amorphous compound powder cores combine the superior DC-Bias properties and the excellent core loss. The core loss of 500 kW/$m^3$ at $B_m$ = 0.1T and f = 100 kHz was obtained When the mass ratio of FeSiB/FeCrMo equals 3:2, and meanwhile the DC-bias properties of the new Fe-based amorphous compound powder cores just decreased by 10% compared with that of the FeSiB powder cores. In addition, with the increasing of the content of the FeCrMo metallic glassy powder, the core loss tends to decrease.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.190-195
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• 2009

Thin-gauged 3% silicon steel sheets having a highly grain-oriented texture have been developed as a core material for applications of middle-frequency (400 Hz ${\sim}$ 10 kHz) devices. The newly developed sheets with a tension coating showed an excellent reduction in iron loss at 400 Hz (iron loss at 1.0 T and 400 Hz = 4.677 W/kg, iron loss at 1.5 T and 400 Hz = 9.742 W/kg) due to high magnetic induction, $B_{10}$(measured induction at 1000 A/m), of over 1.9 T. In cases of frequencies below 400 Hz, magnetic induction, $B_{10}$, of the sample plays a major role to reduce its iron loss as excitation induction increases, whereas, in case of frequency of 1 kHz, thickness dependence becomes dominant due to a lower iron loss at relatively thinner sample. The sheets with a high magnetic induction, therefore, are favorable for high excitation induction (over 1.0 T) and low excitation frequency (below 400 Hz) applications, whereas the sheets that can reduce eddy current loss by reducing thickness or domain wall width are advantageous for low excitation induction (below 1.0 T) and high excitation frequency (around 1 kHz) applications.

• 전자공학회논문지 IE
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• v.46 no.2
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• pp.1-6
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• 2009

The inductor needs to have the desire of super miniaturization, substance of high density and no electronic obstacle. In this study, it analyzes electromagnetic field properties of the core due to inserted high current to develop union type inductor. As the results, it appears high electromagnetic field in inductor insides, but magnetic is very small in inductor surfaces. Also, magnetic distribution are almost 0[T] in circumferences get out of the inductor surfaces. It is an evidence that magnetic distribution as the electronic magnetic obstacle does not appear at other electronic parts. These above results affect to develop the union type inductor, especially it can be expect to help analysis of electromagnetic field properties of inductor core and reliability improvement.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3735-3739
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• 2012

We have developed magnetically controllable gold nanoparticles by synthesizing superparamagnetic $Fe_3O_4$ core/gold shell nanoparticles. The core/shell particles have the capability of forming gold 1D chains in the presence of an external magnetic field. Here we demonstrate dynamic and reversible self-assembly of the gold 1D chain structures in an aqueous solution without any templates or physical or chemical attachment. The spatial configuration of gold chains can be arbitrarily manipulated by controlling the direction of a magnetic field. This technique can provide arbitrary manipulation of gold 1D chains for fabrication purpose. To demonstrate this capability, we present a technique for immobilization of the gold particle chains on a glass substrate.