• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.222-224
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• 1993

In this paper, The optimum oxidation conditions for the formation of Cu-Zn ferrite were investigated using precipitates obtained by the mixture of $CuCl_2{\cdot}2H_2O$, $ ZnCl_2$, $FeCl_3{\cdot}6H_2O$ and NaOH. The precipitates were prepared by coprecipitation method on various temperatures and oxidation conditions. The oxidation products were examined by SEM, XRD, and VSM. The particles obtained at 70($^{\circ}C$) were more spherical and fine than that of prepared at 25($^{\circ}C$), 50($^{\circ}C$), 60($^{\circ}C$), respectively. By $H_2O_2$ oxidation, the saturation magnetization of the powders was little influenced, But, by air oxidation the saturation magnetization of the powders was influenced intricately. According to our experimental data, the saturation magnetization of the powders increased with reaction time and was saturated at 9 hours.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.862-868
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• 2008

Many studies have been conducted to increase heat transfer in fluid. One of the various heat transfer enhancement techniques is suspending fine metallic or nonmetallic solid powder in traditional fluid. Nanofluid is defined as a new kind of heat transfer fluid containing a very small quantity of nanometer particles that are uniformly and stably suspended in a liquid. This study investigates the effect of nanofluid containing diamond, CuNi and CuAg nanometer particles, and proposes the heat transport mechanism of nanofluid. The test result shows that the thermal conductivity of nanofluid is much higher than that of traditional fluid, and the increasing rate of the conductivity is dependent on the conductivity of the solid metal.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1591-1593
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• 1996

The experimental study was carried out to investigate the effects of metallic particulate filler on the mechanical properties and the thermal properties of epoxy resin system filled with Cu powder. As Cu contents increased, the tensile strength, surface hardness and $T_d$ decreased. $T_g$ increased and decreased at 300 phr. $E_d$ decreased and increased at 200 phr, because the thermal conducting path of filler was formed and dissipated thermal stress.

• Progress in Superconductivity
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• v.1 no.2
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• pp.89-94
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• 2000

A YBCO superconductor was prepared in a short time by a melt infiltration process that utilizes meting of $Ba_3Cu5O_8$ powder and the infiltration into a porous $Y_2BaCuO_5$ compact. The processing parameters such as a reaction temperature and time, and atmosphere (air and $O_2$) were controlled to establish the fabrication condition. The formation of a $YBa_2Cu_3O_x$, phase and the developed microstructure are reported.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.403-406
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• 1998

Electroluminescence(EL) come from the light emission obtained by electrical excitation energy passing through a phosphor layer under applied high electrical field. The preparation and characterizations of light emitting ACPEL(alternating-current powder electroluminescent) cell based on two kinds of phosphor mixed ZnS:Mn, Cu and ZnS:Cu phosphor. Basic structure is ITO/Mixed Phosphor/insulator/Al sheet, each layer was mixed by binder, which concentration 11p for phosphor, 8p for insulator. Dielectric properties was investigated first and emission properties of P-LED based on ZnS:Mn,Cu/ZnS:Cu,Br mixture. Emission spectra exhibits two kinds of main peaks at 100V, 1kHz sinusoidal excitation.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.148-149
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• 2015

본 연구에서는 전기 도금법을 이용하여 수 마이크로미터(${\mu}m$)에서 수십 마이크로미터 크기의 수지상(dendrite) 구리분말을 제조하였다. 구리 도금욕의 종류($Cu_2P_2O_7$, $CuSO_4$, $CuCl_2$), 인가 전위(E, Volt) 및 기판에 따른 수지상(Dendrite)의 형상적인 특성이 비교되었으며, 형상에 따른 겉보기밀도와 비표면적 측정(BET)이 진행되었다. 수지상의 2차 가지길이와 주축길이의 비(ratio)를 형상의 차이로 분류한 결과 염화구리 도금욕에서 0.14 로서 가장 큰 값을 가지며 겉보기 밀도는 $1.04g/cm^3$로 가장 낮은 값을 보였다.

• Journal of Welding and Joining
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• v.7 no.3
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• pp.36-43
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• 1989

The furnace brazing in a Ar of copper to martensitic stainless steel(13.5Cr) using Cu-(5~8%)P-(0~8%)Sn powders was investigated. Shear strength, wettability, reacted layer, defect ratio at the stainless steel interface was evaluated. As Sn was added to the Cu-P powders, defect ratio and P content at the stainless steel interface decreased. And also as Sn was added, defect form at the stainless steel interface changed from the continuous layer to the discrete type, and shear strength of the brazed joint increased.

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.280-282
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• 1988

The structural, electrical and magnetic properties were investigated for the high-Tc superconductor $YBa_2Cu_3O_{7-x}$, where x was 0.13. The results of temperature dependence of the resistivity and the magnetization in $YBa_2Cu_3O_{6.87}$ whose structure and phase are confirmed by arialysis of X-ray powder diffraction pattern have been reported. A very sharp superconductivity transition appears at 92K in the specimen whose chemical composition is determined from redox titration, strongly suggesting that this specimen consists of a single-phase superconductor. From the results of X-ray diffraction analysis, magnetization curves, levitation and resistance measurements, it is suggested that the observed superconductivity is bulk property in nature and that the $YBa_2Cu_3O_{6.87}$ phase is responsible for the superconductivity of the present reproducible specimen.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.185-186
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• 2013

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.63-63
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• 2008