• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.68-71
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• 2003

We fabricated Ni-substrate for YBCO coated conductors and evaluated the effects of pressing and annealing time on texture. Ni substrate was fabricated by powder metallurgy technique and compacts were prepared by applying uniaxial or isostatic pressure. The texture of substrate made by applying cold isostatic pressure (CIP) was stronger than that by uniaxial pressure. The texture of substrate made by CIP had a strong 4-fold symmetry and [111] ∥ ND texture after annealing temperature of 100$0^{\circ}C$. It is to be noted that the degree of texture was almost independent of annealing time and the full-width at half-maximum (FWHM) of in-plane and out-of-plane was measured to be in the range of 9.55$^{\circ}$-10.53$^{\circ}$ and 8.57$^{\circ}$-9.85$^{\circ}$, respectively. Development of strong cube texture of Ni-substrate made by powder metallurgy technique in our study is considered to be suitable for the application of YBCO coated conductors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.471.2-471.2
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• 2014

We demonstrate here that an improvement in precursor film density (green density) leads to a great enhancement in the photovoltaic performance of CuInSe2 (CISe) thin film solar cells fabricated with Cu-In nanoparticle precursor films via chemical solution deposition. A cold-isostatic pressing (CIP) technique was applied to uniformly compress the precursor film over the entire surface (measuring 3~4 cm2) and was found to increase its relative density (particle packing density) by ca. 20%, which resulted in an appreciable improvement in the microstructural features of the sintered CISe film in terms of lower porosity, reduced grain boundaries, and a more uniform surface morphology. The low-bandgap (Eg=1.0 eV) CISe PV devices with the CIP-treated film exhibited greatly enhanced open-circuit voltage (VOC, from 0.265 V to 0.413 V) and fill factor (FF, from 0.34 to 0.55), as compared to the control devices. As a consequence, an almost 3-fold increase in the average power conversion efficiency, 3.0 to 8.2% (with the highest value of 9.02%), was realized without an anti-reflection coating. A diode analysis revealed that the enhanced VOC and FF were essentially attributed to the reduced reverse saturation current density (j0) and diode ideality factor (n). This is associated with the suppressed recombination, likely due to the reduction in recombination sites such as grain/air surfaces (pores), inter-granular interfaces, and defective CISe/CdS junctions in the CIP-treated device. From the temperature dependences of VOC, it was confirmed that the CIP-treated devices suffer less from interface recombination.

• 폴리머
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• 제36권5호
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• pp.606-611
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• 2012

Polyetherimide(PEI)와 poly(vinylidene flouride)(PVdF) 폴리머들을 블렌딩하여 전기방사를 통해 웹을 제조하였다. 낮은 기계적 물성을 증대시키기 위해서 압착과 연신이라는 후처리 공정을 이용하였으며 후처리 공정이 기계적 물성에 미치는 영향을 조사하였다. 물리적 특성을 확인하기 위해 SEM, 인장 시험 측정기를 이용하여 측정하였다. $180^{\circ}C$의 압착 온도에서 1/2, 1/3, 1/4, 1/5의 비율로 압착된 웹들은 초기 상태에 비해 대략 4~5배 가량 인장 강도가 증가하였으며, 이들을 $220^{\circ}C$의 온도에서 30~40% 연신함으로써 2~8MPa의 추가적인 인장 강도 증대를 보였다.

• 한국군사과학기술학회지
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• 제22권4호
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• pp.492-500
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• 2019

Equal channel angular pressing(ECAP) is a severe plastic deformation technique capable of introducing large shear strain in bulk metal materials. However, if an ECAPed material has an inhomogeneous microstructure and anisotropic mechanical properties, this material is difficult to apply as structural components subjected to multi-axial stress during use. In this study, extruded oxygen-free copper(OFC) rods with a large diameter of 42 mm are extruded through ECAP by route Bc up to 12 passes. The variations in the microstructure, hardness, tensile properties, and microstructural and mechanical homogeneity of the ECAPed samples are systematically analyzed. High-strength OFC rods with a homogeneous and equiaxed-ultrafine grain structure are obtained by the repeated application of ECAP up to 8 and 12 passes. ECAPed samples with 4 and 8 passes exhibit much smaller differences in terms of the average grain sizes on the cross-sectional area and the tensile strengths along the axial and circumferential directions, as compared to the samples with 1 and 2 passes. Therefore, it is considered that the OFC materials, which are fabricated via the ECAP process with pass numbers of a multiple of 4, are suitable to be applied as high-strength structural parts used under multi-axial stress conditions.

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 2005년도 27회 하계학술발표회 논문집
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• pp.116-139
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• 2005

ICT(information and communication technology) has played a pivotal role in the world economy, and the out look for ICT has improved markedly. One of the noticeable characteristics in the ICT sector Is the global rationalization of its technology and service. Specialization on the specific ICT capability is a pressing problem for many countries. Along the line of classical innovation cluster and network studies, this paper suggests a way to find and analyze the role of core technologies on the ICT network First, technology network is constructed by using patent citation data from USPTO. Then, a couple of cluster is generated by K-means clustering technique. Finally, brokerage analysis is applied to manifest the role of principal technologies. The network visualization and some stylized facts on dynamics are briefly given altogether Based on the role and relationship of technologies across clusters, it is expected that this research could contribute to the ICT cluster formation and the vision-making for ICT specialization at the viewpoint of technology Policy.

• 한국재료학회지
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• 제9권1호
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• pp.92-98
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• 1999

(Mo.W)Si$_2$ composites were fabricated by vacuum hot-pressing elemental Mo, W and Si powders at various temperatures. Elemental Mo, W and Si powders were alloyed in the proper proportions to form solid solutions. The microstructure and properties of these materials was characterized by using x-ray diffraction, optical microscopy, energy dispersive x-ray spectroscopy and Vicker's technique. It was found that tungsten was mainly substituted for Mo atoms, and made a completed solid solution of (Mo.W)Si$_2$ over 1$600^{\circ}C$. The lattice parameters and Vickers hardness increased largely with increasing reaction temperature by the most soluble elements, due to the solid-solution hardening.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1136-1141
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• 2003

Among various methods to manufacture the PDP barrier ribs, the pressing and the roll forming methods are simple and economical because they form the ribs by utilizing the plastic flow of the green tape in a relatively short time without generating air-polluting dusts. In the present study, the roll forming method was investigated by experiments as well as numerical analyses and in result the groove roll and the preform were designed. The effect of draft angle, comer radius, and initial thickness of the green tape on the plastic flow was examined by a series of parametric studies. The preform was recommended to ease the plastic flow into the grooves and to avoid the occurrence of crack during rolling and sintering processes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.329-332
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• 2002

The upper bound analysis by stream function is used to study the torsional forward extrusion. The torsional forward extrusion process not only reduces forming load but also increase optimal die angle. Optimal die angle is determined by the optimization technique. The advantages of this process are that the low capacity of pressing machine can be used and the process with a large die angle can be applied. To verify the theoretical result, we have carried out experiments using model material (plasticine) and FE simulations using DEFORM3D.

• 한국재료학회지
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• 제13권9호
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• pp.561-566
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• 2003

Mechanical alloying(MA) process using elemental powders followed by hot pressing has been applied to some intermetallic alloy system containing ferromagnetic elements, such as NiAl and $FeSi_2$. A modified thermogravimetric analysis (TGA) technique was used to investigate the degree of alloying in milled powders and hot consolidated specimens as well as heat-treated bulk specimens. It is shown that the measurement of Curie temperatures in MA intermetallic powders and consolidated specimens containing ferromagnetic components, when determined as a function of milling and heat treatment parameters, can give some insight into the progress and mechanism of alloying.

• 한국세라믹학회지
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• 제42권12호
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• pp.860-864
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• 2005

In this study, we fabricated honeycomb type Mixed-Gas Fuel Cell (MGFC) which has advantages of stacking to the axial direction and increasing volume power density. Honeycomb-shaped anode with four channels was prepared by dry pressing method. Two alternative channels were coated with electrolyte and cathode slurry in order to make cathodic reaction sites and the others were filled with partial oxidation (POX) catalyst to increase fuel conversion. Furthermore we employed the sol-gel technique which can increase cell performance and decrease carbon coking.