• Electrical & Electronic Materials
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• v.9 no.1
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• pp.76-92
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• 1996

본 고에서는 대표적인 연자성재료인 Soft 페라이트, 퍼멀로이, 센더스트와 비정질 자성합금계의 특성과 용도를 살펴봄으로써 현재의 기술현황을 알아보고 그 문제점 해결과 특성개선을 위한 연구동향에 대하여 검토하여 보기로 한다. 또한 연자성재료 일반에 걸쳐 용도별 분류와 각 응용기술 분야에서의 기술동향 및 전망에 대하여 소개하고자 한다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.446-447
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• 2006

Magnetic oxide-coated iron nanoparticles with the mean size ranging from 6 to 75 nm were synthesized by aerosol method using iron carbonyl as a precursor under the flowing inert gas atmosphere. Oxide shells were formed by passivation of asprepared iron particles. The influence of experimental parameters on the nanoparticles' microstructure, phase composition and growth behavior as well as magnetic properties were investigated and discussed in this study.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.451-452
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• 2006

The influence of Hi-flux powders characteristics on the performance of magnetic powder cores was studied. It was found that different cooling rate and nozzle configuration could change the shape and microstructure of powders. Smooth surface and spherical shape of powders were beneficial to improve DC bias performance and reduce core losses of magnetic powder core.

• Journal of Magnetics
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• v.5 no.2
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• pp.59-64
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• 2000

A drum type of high gradient magnetic separator was designed and optimized by computer simulations. The magnetic separator consists of high performance rare earth $(Nd_2Fe_14B)$ permanent magnets and magnetic yokes of extremely low carbon steel interconnecting the permanent magnets. Magnetic circuits of the separator were simulated for the aim of the least cost, highest magnetic strength and most efficient function by using specialized S/W (Vector Field Program) employing the Finite Element Method. The magnetic flux density was provided to be strong enough to collect the invisible fine metal particles from the surface of hot rolled steel plate with the efficiency of almost 95%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.537-540
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• 2003

This study was investigated to fabricate the porcelain materials with high magnetic characteristics. The high characteristics of the magnetic porcelain materials were achieved at the following conditions; powder sizes of isotropic Sr-ferrites with $1{\sim}2\;mm$ and magnetic powder infraction of 30 wt%. The magnetic tea cups with 3-mm-thick at the optimum conditions indicated the high magnetic characteristics such as the surface flux density of 178 G, the remanent flux density of 240 G, and the intrinsic coercivity of 3910 Oe.

• Journal of Magnetics
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• v.16 no.2
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• pp.134-139
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• 2011

Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.88-91
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• 2003

The magnetic porcelain materials were studied by using the porcelain materials added Sr-ferrite powders before forming and firing process. For the high magnetic property, the Sr-ferrite magnetic powders with the grain size of 1 ${\mu}m$ were agglomerated the powder size of about 1 mm. The magnetic porcelain with 30 wt% of Sr-ferrite powders indicated the magnetic characteristics such as the remanent flux density of 240 G and the intrinsic coercivity of 3910 Oe, at the firing conditions of $1250^{\circ}C$/1hr in air.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.25-27
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• 1998

In this paper electromagnetic force and its distribution are analyzed on the nonlinear magnetic materials by Finite Element Method. Most of magnetic materials have the nonlinear characteristic, which considerably effects on the magnetic system. And it is necessary to know its distribution at the every Part of the magnetic material in order to design the, magnetic system considering noise, vibration and strain characteristic. The results are obtained by Maxwell stress. virtual work and magnetic charge method and compared with one another.

• Journal of Powder Materials
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• v.23 no.5
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• pp.391-396
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• 2016

In this study, ultra-fine soft-magnetic micro-powders are prepared by high-pressure gas atomization of an Fe-based alloy, Fe-Hf-B-Nb-P-C. Spherical powders are successfully obtained by disintegration of the alloy melts under high-pressure He or $N_2$ gas. The mean particle diameter of the obtained powders is $25.7{\mu}m$ and $42.1{\mu}m$ for He and $N_2$ gas, respectively. Their crystallographic structure is confirmed to be amorphous throughout the interior when the particle diameter is less than $45{\mu}m$. The prepared powders show excellent soft magnetic properties with a saturation magnetization of 164.5 emu/g and a coercivity of 9.0 Oe. Finally, a toroidal core is fabricated for measuring the magnetic permeability, and a ${\mu}_r$ of up to 78.5 is obtained. It is strongly believed that soft magnetic powders prepared by gas atomization will be beneficial in the fabrication of high-performance devices, including inductors and motors.

• Journal of Magnetics
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• v.18 no.3
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• pp.245-249
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• 2013

A finite element model was built for MnBi/${\alpha}$-Fe nanocomposite permanent magnets, and the demagnetization curves of the magnets were simulated by micro-magnetic calculation. The microstructure of the cubic model is composed of 64 irregular grains with an average grain size of 20 nm. With the volume fraction of soft magnetic phase (t vol. %) ranged from 5 to 20 vol. %, both isotropic and anisotropic nanocomposite magnets show typical single-phase permanent magnets behavior in their demagnetization curves, illustrating good intergranular exchange coupling effect between soft and hard magnetic phases. With the increase of volume fraction of soft magnetic phase in both isotropic and anisotropic magnets, the coercive force of the magnets decreases monotonically, while the remanence rises at first to a peak value, then decreases. The optimal values of maximum energy products of isotropic and anisotropic magnets are 84 and $200kJ/m^3$, respectively. Our simulation shows that the MnBi/${\alpha}$-Fe nanocomposite permanent magnets own excellent magnetic properties and therefore good potential for practical applications.