• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.183-187
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• 2007

$SiO_2/TiO_2$ core-shell particles with controlled shell thickness were prepared using large silica particles. The thickness of titania coating layer was varied from 8 nm to 38 nm depending on the number of coating steps from 1 to 3 times. After titania coating, the core-shell particles showed textured surface due to the titania coating layer, resulting in 3~25 times increase of specific surface areas. The properties of titania coated silica particles were characterized by FE-SEM, Zeta potential meter, BET, and XRD.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.233-233
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• 2013

유기물/무기물 나노복합체를 이용하여 제작한 비휘발성 메모리 소자는 간단한 공정과 플렉서블 기기 응용 가능성 때문에 많은 연구가 진행되고 있다. 다양한 나노입자를 포함한 고분자 박막에 대한 연구는 많이 진행되었지만, 비휘발성 메모리소자에서 CdSe/InP 나노입자를 사용한 나노복합체의 전기적 안정성과 동작 메커니즘에 대한연구는 미흡하다. 본 연구는 CdSe/InP 코어/쉘 나노입자가 poly (N-vinylcarbazole) (PVK) 박막에 분산되어 있는 나노복합체를 이용하여 메모리 소자를 제작하여 전기적 특성과 안정성을 관찰 하였다. 소자 제작을 위해PVK 고분자를 용매인 클로로벤젠에 용해한 후, 헥산에 안정화 되어있는 CdSe/InP 나노입자를 초음파 교반기를 사용하여 고르게 섞었다. Indium-tin-oxide (ITO)가 증착한 유리 기판을 화학물질로 세척한 후 기판 위에 CdSe/InP 나노입자와 절연성 고분자인 PVK가 혼합된 용액을 스핀코팅 방법으로 도포하여 나노입자가 포함된 고분자 박막층을 형성하여 저항 변화층으로 사용하였다. 형성된 박막 위에 마스크를 사용하여 Al 상부전극을 고진공에서 열 증착하여 비휘발성 메모리 소자를 제작하였다. 제작된 소자의 전류-전압(I-V) 특성을 측정한 결과 동일전압에서 전도도가 좋은 상태 (ON)와 좋지 않은 상태 (OFF)인 두 개의 상태상 존재한다는 것을 확인하였고, CdSe/InP인 나노입자가 포함된 소자와 포함되지 않은 소자의 전기적 특성을 비교 분석하였다. 두 상태의 안정성을 ON 또는OFF 상태의 스트레스를 측정하여 두 상태의 안정성을 확인하였고, 실험결과를 바탕으로 메모리 소자의 동작 메커니즘을 기술하였다.

• KSBB Journal
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• v.24 no.1
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• pp.1-8
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• 2009

In the past decade, we have observed rapid advances in the development of biochips in many fields including medical and environmental monitoring. Biochip experiments involve immobilizing a ligand on a solid substrate surface, and monitoring its interaction with an analyte in a sample solution. Metal nanoparticles can display extinction bands on their surfaces. These charge density oscillations are simply known as the localized surface plasmon resonance (LSPR). The high sensitivity of LSPR has been utilized to design biochips for the label-free detection of biomolecular interactions with various ligands. LSPR-based optical biochips and biosensors are easy to fabricate, and the apparatus cost for the evaluation of optical characteristics is lower than that for the conventional surface plasmon resonance apparatus. Furthermore, the operation procedure has become more convenient as it does not require labeling procedure. In this paper, we review the recent advances in LSPR research and also describe the LSPR-based optical biosensor constructed with a core-shell dielectric nanoparticle biochip for its application to label-free biomolecular detections such as antigen-antibody interaction.

• Polymer(Korea)
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• v.33 no.5
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• pp.463-468
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• 2009

Syntheses of monodisperse and micron-sized hollow plastic pigment (HPP) were carried out through the core-shell reaction. The effects of the reaction parameters, such as the particle size, molecular weight, the swelling time, agitation rate, and the solid contect were investigated. This micron-sized HPP could be made by using the alkali soluble core with at least bigger than 200 nm size. To obtain a higher opacity ratio, the swelling time and molecular weight of the core should be controlled. The agitation rate affected the particle's morphology. To prevent the shell destruction, the agitation rate must be sufficiently low in case of the syntheses of micron-sized HPP. In this study, micron-sized HPP exhibiting the high hiding power and narrow particle distribution could be obtained.

• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.273-273
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• 2010

최근 들어 에너지 개발과 환경문제의 해결방안으로 열전발전 및 열전냉각에 많은 관심과 연구가 진행되고 있다. 열전소재의 특성 향상을 위해 열전성능지수를 높이기 위하여 나노 입자상을 열전소재 내에 분산하고자 하는 연구가 진행되었다. Grain 내에 나노 입자를 분산하기 위해서는 원료 입자에서부터 나노 입자가 열전소재 내에 분산되어야 하며 이것은 산화물 나노입자의 코어-쉘 형성으로부터 가능하다. 이 과정에서 나노 입자를 열전소재 내에 코어로 분산하기위한 나노입자의 합성 및 제어가 필수적이다. 본 연구에서는 용융염법을 이용한 BaTiO3 나노 일자를 합성하고 이들을 용매에 분산하는 것을 목표로 하였다. 염으로는 KCl, LiCl, NaCl 및 이들의 혼합 염을 사용하였으며 염의 청가량, 염의 종류, 반응온도 및 반응시간의 변화에 따라 BaTiO3 나노 입자를 합성하였다. 또한, 합성된 나노 입자의 입자크기와 응집 제어를 통해 나노입자들의 분산 상태를 확인해 보았다. 이 결과는 SEM, TEM, 입도측정기, XRD등의 측정 결과를 통하여 확인하고자 하였다.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.111-112
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• 2009

• Polymer(Korea)
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• v.33 no.5
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• pp.485-489
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• 2009

The temperature dependence of the structure of micelles formed by a deuterated polystyrene-poly(ethylene oxide) diblock copolymer (dPS-PEO) in heavy water were investigated with small-angle neutron scattering (SANS). SANS data were analyzed using the hard-sphere structure factor in combination with the form factor of a core-shell model. The micelle aggregation number and corona radius were obtained from the fits to the SANS data. The micelle aggregation numbers varied with temperature from 229 at $25^{\circ}C$ to 240 at $45^{\circ}C$, with a corresponding increase in the core radius. However, the shell thickness of micelles decreased with increasing temperature from 6.2 to 5.8 nm. These structural changes of micelles might be ascribed to the decrease in the hydration volume per hydrophilic group in the corona because of the increase in hydrophobicity of the PEO block with increasing temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.6
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• pp.663-668
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• 2017

SOFC anode fabricated core-shell using machano-fusion method using core with submicron size Ni, nano size YSZ for shell. Using prepared core-shell, depending on the thickness of the shell, we studied how the characteristics of sintering and SOFC cell change by sintering the anode. The Ni-YSZ core-shell has a Ni core of 0.5 to $1.2{\mu}m$ over 2 to 7 YSZ of 15 to 20 nm is, and as the high speed mixing time increases, the YSZ number increases and the shell thickness becomes uniform increased. When the fuel electrode is manufactured with core-shell, it has superior sintering property, has grain of uniform size compared with the one synthesized by general mixing, the falling path is short, the conductors (electrons and ions) connection is excellent, the electrical conductivity has become excellent. The thicker the shell, the lower the electrical conductivity. When the thickness of shell ranged from 46 to 139 nm and 61 to 81 nm, the performance was the highest and the ASR was the smallest.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.382-388
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• 2010

This paper describes the standardized finite element model for carbody structures of railway vehicle made of sandwich composites. Recently, sandwich composites were widely used to railway vehicle due to the improvement of energy efficiency, high specific stiffness and strength, weight reduction and space saving in korea. Therefore, structural integrity should be verified using finite element analysis prior to the manufacture of composite railway vehicle. The standardized finite element model for composite carbody structures was introduced through comparing the results of real structural test under vertical, compressive, twisting load and natural frequency test of various railway vehicles in this study. The results show that the quadratic shell element is suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panel compared to beam element, and layered shell and solid element are recommended to model the skin and honeycomb core of sandwich panel compared to sandwich shell element. Also, the proposed standard finite element model has the merit of being applied to crashworthiness problem without modifications of finite element model.