• Journal of Powder Materials
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• v.16 no.4
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• pp.291-295
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• 2009

The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.

• Advances in nano research
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• v.10 no.1
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• pp.77-90
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• 2021

In the present study, novel chitosan coated magnetic magnetite (Fe3O4) nanoparticles were successfully biosynthesized from mushroom, Agaricus campestris, extract. The obtained bio-nanocomposite material was used to investigate ultra-fast and highly efficient for removal of Ni2+ ions in a fixed-bed column. Chitosan was treated as polyelectrolyte complex with Fe3O4 nanoparticles and a Fungal Bio-Nanocomposite Material (FBNM) was derived. The FBNM was characterized by using X-Ray Diffractometer (XRD), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infrared spectra (FTIR) and Thermogravimetric Analysis (TGA) techniques and under varied experimental conditions. The influence of some important operating conditions including pH, flow rate and initial Ni2+ concentration on the uptake of Ni2+ solution was also optimized using a synthetic water sample. A Central Composite Design (CCD) combined with Response Surface Modeling (RSM) was carried out to maximize Ni2+ removal using FBNM for adsorption process. A regression model was derived using CCD to predict the responses and analysis of variance (ANOVA) and lack of fit test was used to check model adequacy. It was observed that the quadratic model, which was controlled and proposed, was originated from experimental design data. The FBNM maximum adsorption capacity was determined as 59.8 mg g-1. Finally, developed method was applied to soft drinks to determine Ni2+ levels. Reusability of FBNM was tested, and the adsorption and desorption capacities were not affected after eight cycles. The paper suggests that the FBNM is a promising recyclable nanoadsorbent for the removal of Ni2+ from various soft drinks.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.40-42
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• 2006

연자성 복합재료는 기존의 철판 대비 기계적, 자기적 특성 떨어지는 것이 사실 이였다. 본 연구에서는 이러한 문제점 개선을 위해서 저점도 윤활제 적용을 통한 빼기 압력 저감 방안을 도출하였다. 연자성체의 고강도화, 우수한 자기적 특성을 얻기 위해서 높은 압력의 성형이 필수적인데 높은 압력으로 성형시 빼기 압력이 높아져서 금형이 파손되는 등 문제점으로 인해 우수한 특성을 얻을 수 없었다. 본 연구에서는 이러한 문제점을 해결하기 위해서 저 점도액체 윤활제, 고점도 액체 윤활제, 고체 윤활제 3가지의 윤활제 특성을 검토 하였다. 또한 저점도 액체 윤활제 적용을 통해서 기존 대비 강도 10%, 철손 10%, 빼기 압력 30%를 저감 하였다.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.43-44
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• 2007

SMC(Soft Magnetic Composite) 재질은 일반 실리콘 강판에 비해 코어의 3차원 형상을 자유롭게 제작 할 수 있으며, 고속 회전시에 발생하는 철손을 감소시킬 수 있어 모터 코어용으로 많은 제작이 이루어지고 있다. 따라서 본 논문에서는 고속 회전용 청소기용 BLDC 모터의 코어를 SMC 재질로 제작 Back-EMF를 측정하였다. 코어의 형상은 크게 3차원 형상을 고려한 3가지로 타입으로 구분하여 제작하였고, 각 형상별로 모터를 제작하여 특성을 측정하였다. 본 논문에서는 SMC 분말을 이용한 코어 성형시 3차원 형상에 따른 모터의 Back-EMF의 특성을 보여준다.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.589-591
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• 2008

본 논문은 연자성체(Iron powerder)인 일명 SMC(Soft Magnetic Composite)를 적용한 3상 BLDC motor의 설계 및 제작, 측정에 관한 연구이다. 특히 본 연구에서는 냉장고 압축기용 120W급 3상 BLDC motor에 관한 것으로써 연자성체를 적용시 모터 특성결과에 대하여 기술하였다. 아울러 SMC를 이용한 모터설계의 기준을 제시하였다. SMC 재질은 일반 실리콘 강판에 비해 코어의 3차원 형상을 자유롭게 제작 할 수 있으며, 고속 회전시 발생하는 철손을 감소시킬 수 있어 모터 코어용으로 많은 연구가 이뤄지고 있다. 따라서 본 논문에서는 우선 2차원 설계를 통하여 냉장고 압축기용 BLDC motor의 코어를 SMC 재질로 제작 성능 측정 하였다.

• Applied Microscopy
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• v.45 no.2
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• pp.52-57
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• 2015

Bulk metallic glass (BMG) shows higth strength, high elastic limit, corrosion resistance and good wear resistance and soft magnetic properties and has been considering as a candidate for new structural materials. But they show limited macroscopic plasticity and lack of tensile ductility due to highly localized shear deformation, which should be solved for real structural application. In this paper researches on the enhancement of plasticity of BMG were reviewed briefly. Introducing heterogeneous structure in glass is effective to induce more shear transformation zones (STZs) active for multiple shear band initiation and also to block the propagating shear band. Several methods such as BMG alloy design for high Poisson's ratio, addition of alloying element having positive heat of mixing, pre-straining BMG and variety of BMG composites have been developed for homogenous distribution of locally weak region, where local strain can be initiated. Therefore enhancement of plasticity of BMG is normally accompanied with some penalty of strength loss.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1442-1443
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• 2006

본 논문에서는 분말 연자성체에 플라즈마를 이용하였을 때 특성 개선에 관한 연구이다. 기존의 압분 방식은 낮은 강도를 갖는 단점 때문에 신뢰성에 문제가 있어서, 직접적인 모터분야에 연자성체(SMC)를 적용하는데 큰 문제점 이였다. 그러나 본 논문에서 제안하는 SPS(Spark Plasma sintering)공법을 적용한 모터 코어 제조 방법은 플라즈마를 이용하여 분말의 표면에서만 접촉이 일어나게 하는 소결 방식으로, 내부재질의 특성변화 없이 표면의 절연층끼리만 접촉되게 하여 자기적 특성의 손상없이 기계적인 강도를 높일 수 있었다. 실제적으로 기존의 압분체(Hoganass550+윤활제(KE))의 경우 파단강도가 700Mpa정도였으나 SPS를 적용시 1200Mpa까지 증가 되었다. 이러한 SPS 공법을 통해 연자성체(SMC)재질의 모터 Core 분야 적용하는 데 생기는 문제점을 해결하고자 하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.57-63
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• 2012

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1029-1030
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• 2007

This paper describes the dynamic analysis method and the characteristics of rotating type transverse flux motors excited by permanent magnets; the machine is called TFRM in here. A prototype of TFRM, made by combing soft magnetic composite (SMC) core, is introduced first, then the magneto static and dynamic analysis methods are explained. Analysis results are compared with measured results, and finally the effects of the proposed dynamic analysis method and the characteristics of TFRM are discussed.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.225-230
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• 2011

Magnetic materials has been applied to various fields due to their energy convertible properties between electrical and mechanical energy. Particularly, permanent magnets have been currently attracted much attention because they produce external magnetic field without any electrical current. For high efficiency, a demand for permanent magnets containing rare earth elements has been continuously increased, which abruptly raises the price and causes the supply difficulty of rare earth materials. Therefore, the development of permanent magnets with less or without rare earth elements become a urgent issue. In this report, the current trend and major issues on high efficiency permanent magnets, particularly exchange-coupling magnets, are discussed.