• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.420-421
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• 2006

In the present study, ultrafined Zr-V-Fe based alloy powder prepared by a plasma arc discharge process with changing process parameters. The chemical composition of synthesized powder was strongly influenced by the process parameters, especially the hydrogen volume fraction in the powder synthesis atmosphere. The synthesized powder had an average particle size of 50 nm. The synthesized Zr-V-Fe based particles had a shell-core structure composed of metal in the core and oxidse in the shell.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1591-1599
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• 2017

In power electronics applications which switching frequency is below audible frequency, the acoustic noise and vibration design of magnetics are as important as the efficiency. In the case of the powder core, which is widely used in grid-connected inverters, many researches have been progressed in terms of efficiency. However, there are only few research have been progressed related with acoustic noise and vibrations. In this paper, the Sendust(Fe-Si-Al) powder core material which has low magnetostriction and low core loss is analyzed in terms of acoustic noise and vibration induced by Maxwell force and magnetostriction. Three building structures such as, rectangular, toroidal, and oval shape are designed for 4kW grid-connected inverter, because magnetic properties and the audible noises of the inductor are varied by magnetic core building structures. The effects of the Maxwell force and magnetostriction behaviors varied with core shapes are analyzed by finite element method and experiments. In addition, experiment results of the inductor efficiency are presented according to core building structures.

• Journal of Magnetics
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• v.20 no.2
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• pp.138-147
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• 2015

The unique nano-scale inter-lamellar microstructure and unparalleled heat treatment process give our developed metal powder composite its outstanding magnetic property for power inductor & motor applications. Compared to the conventional polycrystalline Fe or amorphous Fe-Cr-Si-B alloys, our unique designed inter-lamellar microstructure strongly decreases the intra-particle eddy current loss at high frequencies by blocking the mutual eddy currents. The combination of optimum permeability, magnetic flux and extremely low core loss makes this powder composite suitable for high frequency applications well above 10 MHz. Moreover, it can be also possible to SMC core for high speed motor applications in order to increase the motor efficiency by decreasing the core loss.

• Journal of Magnetics
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• v.22 no.1
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• pp.100-103
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• 2017

We studied the microstructure and magnetic properties of Fe nanosized powder synthesized by the pulsed wire evaporation method. The x-ray diffraction spectrum confirmed that this powder had a pure ${\alpha}$-Fe phase. Scanning electron microscope and transmission electron microscope measurements indicated that the prepared powder had uniform spherical shape with core-shell structure. The mean powder size was about 35 nm and the thickness of the surface passivation layer was about 5 nm. Energy dispersive X-ray spectroscopy measurement indicated that the surface passivation layer was iron oxide. Magnetic field dependent magnetization measurement at room temperature showed that the maximum magnetization of the prepared powder was 177.1 emu/g at 1 T.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.160-161
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• 2006

Seasonal changes have been recognized in particle characteristics and forming characteristics of iron powder with insulated coating for a compacted magnetic core because of its high hygroscopicity, due to its phosphate coating and resin binder additives. For this reason, particle characteristics and molding characteristics of the powder with diverse water absorbtivity have been studied. The result shows that the higher the volume of absorbed water, the worse the fluidity becomes, resulting in the reduction in both springback during the molding process and expansion reduction after the heat treatment. The requirement on dimension accuracy for the finished product can be satisfied with an additional drying process on the material powder, which contributes to maintain its water volume constant.

• Journal of Powder Materials
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• v.25 no.5
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• pp.402-407
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• 2018

Molybdenum silicide has gained interest for high temperature structural applications. However, poor fracture toughness at room temperatures and low creep resistance at elevated temperatures have hindered its practical applications. This study uses a novel powder metallurgical approach applied to uniformly mixed molybdenum silicide-based composites with silicon carbide. The degree of powder mixing with different ball milling time is also demonstrated by Voronoi diagrams. Core-shell composite powder with Mo nanoparticles as the shell and ${\beta}-SiC$ as the core is prepared via chemical vapor transport. Using this prepared core-shell composite powder, the molybdenum silicide-based composites with uniformly dispersed ${\beta}-SiC$ are fabricated using pressureless sintering. The relative density of the specimens sintered at $1500^{\circ}C$ for 10 h is 97.1%, which is similar to pressure sintering owing to improved sinterability using Mo nanoparticles.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.31.2-31.2
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• 2011

We studied a method of manufacturing an anode to restrict contraction in reducing NiO/YSZ by uniformly mixing. In order to mix Ni and YSZ, a sub-micron Ni core surface was coated at high-speed by a mixture of nano-sized YSZ and a spherical core-shell was subsequently formed. The micron-sized core-shell anode powder was then heat treated at $400{\sim}1,450^{\circ}C$ in an air atmosphere and Ni was extruded and synthesized in nano-size. Subsequently, when the nano-sized mixture of the anode was heat treated and maintained at a temperature of $1,450^{\circ}C$, the anode was manufactured, where Ni and YSZ were uniformly distributed with the nano-structure. According to the nano-sized anode powder synthesis process, Ni particles were oxidized at $400{\sim}500^{\circ}C$ and became spherical by surface tension. In the case of the spherical core Ni powder, the heat treatment temperature rose to $1,250^{\circ}C$ and then a gap between the internal and external pressures occurred due to thermal and tensile stresses. A crack subsequently appeared on the surface, and the heat treatment temperature was increased continuously to increase the pressure gap and then the core Ni extruded as a nano-sized powder, Ni and YSZ uniformly distributed. It was found that the anode of 50~200 nm with a consistent structure obtained in this study has electric conductivity that is approximately 3 times larger than that of a commercial anode.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.798-798
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• 2006

• The Journal of Korean Medical History
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• v.33 no.1
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• pp.113-125
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• 2020

This paper analyzes information on Augmented Widen the Core Powder (加味普正散) (AWCP) in the Dr. Kim Young Hoon's medical record database, Cheongang Medical Records. AWCP is a prescription that is not found in the existing medical texts, yet is referred to in Dr. Kim Young Hoon's medical record database. By examining these records, this study shows that the original prescription for AWCP was Decoction for Rectifying the Qi with Cyperus and Kudzu (香葛正氣飮) and that this prescription was deeply related to Rectify the Qi Powder Worth More Than Gold (不換金正氣散) as well as Cyperus and Kudzu Decoction (香葛飮). In addition, AWCP had several names over a long period of time, and its name changed from the Powder of Relieving Lives and Rectifying the Qi (普救正氣散) to AWCP. In particular, this study shows that the term 'gami' (加味 augmented) indicates a change in prescription name, not a change in the composition of the prescription.

• Journal of Powder Materials
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• v.21 no.6
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• pp.441-446
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• 2014

In this study, we synthesize silica-core gold-satellite nanoparticles (SGNPs) for the surface-enhanced Raman scattering (SERS) based sensing applications. They consist of gold satellite nanoparticles (AuNPs) fixed on the silica core nanoparticles, which sizes of AuNPs can be tunned by varying the amount of reactants (growth solution and reducing agent). Their surface plasmon resonance (SPR) properties were characterized by using UV-vis spectroscopy, showing that the growth of AuNPs on silica cores leads to the light absorption in the longer wavelength region. Furthermore, the size increase of AuNPs exhibited the dramatic change in SERS activity due to the formation of hot spots. The optimized SGNPs showing enhancement factor ${\sim}3.8{\times}10^6$ exhibited a detection limit of rhodamine 6G (R6G) as low as $10^{-8}M$. These findings suggest the importance of size control of SGNPs and their SPR properties to develop highly efficient SERS sensors.