• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.83-88
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• 2010

The composite electroplating is accomplished by adding inert materials during the electroplating. Permalloy is the term for Ni-Fe alloy and it is used for industrial applications due to its high magnetic permeability. Microhardness for microdevices is enhanced after composite coating and it increases the life cycle. However, the hydroxyl group on the silica makes their surface susceptible to moisture and it causes the silica nanoparticles to be agglomerated in the aqueous solution. The agglomeration problem causes poor dispersion which eventually interrupts uniform deposition of silica nanoparticles. In this study, the dispersion of silica nanoparticles in the permalloy electroplated layer is reported with variation of additives and sonication time. Longer sonication period guaranteed better silica nanopowder dispersion and sonication period also influenced on composition of deposits. The amount of silica nanopowder codeposition and surface morphologies were influenced with variation of additives. In alkaline bath, smooth surface morphology and relatively high contents of silica nanopowder codeposition were obtained with addition of sodium lauryl sulfate.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.50-50
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• 2006

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.76-79
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• 2007

From the previous researches about flow characteristic of micro-nozzle， we found that viscosity and back pressure induced heavy losses in micro nozzle. To overcome thess losses, we began to study new conceptual micro propulsion system that is thermal transpiration based micro propulsion system. It has no moving parts and can pump the gaseous propellant by temperature gradient only (cold to hot). Most of previous research on thermal transpiration is in its early stage and mainly studied for application to small vacuum facility or gas chromatography in ambient condition using nanoporous material like aerogel. In this study, we focus on basic research of propulsion system based on thermal transpiration using polyimide material in vacuum conditions.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.556-561
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• 2021

Recently, iron oxide nanoparticles have been used as the subject of many studies on drug delivery system (DDS) due to their excellent magnetic properties and biocompatibility in response to external magnetic fields. In this study, hyaluronic acid-superparamagnetic microneedles (HA-SMNs) and carboxy methyl cellulose-superparamagnetic microneedles (CMC-SMNs) containing superparamagnetic iron oxide nanoparticles (SIONs) were prepared with HA and CMC as a matrix materials of MNs (microneedles). Various properties of SMNs were then investigated with scanning electron microscopy (SEM), superconducting quantum interference device-vibrating sample magnetometer (SQUD-VSM), frequency mixing magnetic detection (FMMD), and polymer/bio membrane. The SQUID-VSM measurements showed superparamagnetism of HA-SMNs and CMC-SMNs containing SIONs. The FMMD results demonstrated that the signal intensity changed significantly as the concentration of SIONs increased. In addition, SMNs exhibited the average skin permeability intensities on the bio membrane for HA-SMNs and CMC-SMNs were 92.5 and 98.5%, respectively. These results suggested that SMNs could be utilized as deliver materials for a TDDS and MR molecular imaging.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.126.1-126.1
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• 2011

박막형 태양전지의 효율 향상을 위하여 광확산 패턴이 형성된 기판을 제작하고 이를 이용하여 비정질 실리콘 박막 태양전지를 제작하였다. 나노 임프린트 방법을 사용하여 제작된 광확산 패턴은 불규칙한 마이크로-나노 크기의 미세구조를 가지고 있어 빛의 확산투과 비율을 향상시켜주는 역할을 하였다. 제작된 광확산 기판위에 TCO물질을 증착하고, PECVD법을 사용하여 비정질 실리콘 p-i-n 접합 구조를 형성하였다. 제작된 태양전지 소자를 1.5 AM의 조건에서 I-V 특성을 분석하였으며, 비교군으로 사용된 일본 Asahi 사의 U-type glass에 비해 높은 Jsc 값을 나타내었다. 또한 외부양자효율을 측정함으로써 광확산 패턴에 의한 양자효율 변화를 확인 할 수 있었다.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.162-167
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• 2006

Hot embossing lithography(HEL) has the production advantage of comparatively few process step, simple operation, a relatively low cost for embossing tools(Si), and high replication accuracy for small features. In this paper, we considered the nano-molding characteristic according to molding parameters(temperature, pressure, times, etc) and induced a optimal molding condition using HEL. High precision nano-patter master with various shapes were designed and manufactured using the DRIE(Deep Reactive ion Etching), LPCVD(Low Pressure Chemical Vapor Deposition) and thermal oxidation process, and we investigated the molding characteristic of DVD and Blu-ray nickel stamp. We induced flow behaviors of polymer, rheology by shapes and sizes of the pattern through various molding experiments. Finally, with achieving nano-structure molding with high aspect ratio, we will secure a basic technology about the molding of large-area nano-pattern media.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.4
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• pp.39-42
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• 2011

The composite electroplating is accomplished by adding inert materials during the electroplating. Permalloy is the term for Ni-Fe alloy and it is used for industrial applications due to its high magnetic permeability, surface wear resistance, corrosion protection. Microhardness for microdevices is enhanced after composite coating and it increases the life cycle. However, the hydroxyl group on the silica makes their surface susceptible to moisture and it causes the silica nanoparticles to be agglomerated in the aqueous solution. The agglomeration problem causes poor dispersion which eventually interrupts uniform deposition of silica nanoparticles. In this study, the dispersion of silica nanoparticles in the permalloy electroplated layer is reported with variation of additives and current densities. The optimum current density was 20 $mA/cm^2$ and the silica content was 9 at% at $50^{\circ}C$. The amount of silica nanopowder codeposition and surface morphologies were influenced with variation of additives. In the bath, smooth surface morphology and relatively high contents of silica nanopowder codeposition were obtained with addition of sodium lauryl sulfate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.217-217
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• 2008

$BaTiO_3$는 perovskite 구조를 가지는 대표적인 강유전체 재료로서 MLCC (Multi Layer Ceramic Capacitor), PTC thermistor 등에 널리 사용되어지고 있으며, 그 특성을 향상시키기 위하여 많은 연구가 진행되고 있다. 현제 $BaTiO_3$ 분말 제조의 대표적인 합성법으로는 하소와 분쇄공정이 없는 수열합성법이 대표적이나, 나노 사이즈로 제작시 $BaTiO_3$는 마이크로 크기와 달리 입방정상으로 우세한 상태로 존재한다. 이는 제조과정 중의 hydroxyl defect의 영향과 나노 분말의 표면에너지 증가 때문이라고 보고된다. 따라서 본 연구는 이러한 문제점을 해결하기 위해 일반적인 세라믹 제조 방법인 고상반응법을 이용한 나노 사이즈의 $BaTiO_3$ 제조를 위한 최적의 공정 조건을 확립하기 위하여 본 연구를 진행하였다. 조성은 $BaTiO_3$와 반응온도를 낮추기 위한 anatase의 $TiO_2$를 사용하였고, $BaCO_3/TiO_2$ 의 조성비 (1. 1.01, 1.02, 1.03)를 제어하여 혼합한 후, 24h ball-mill 하여 하소 온도 ($860^{\circ}C{\sim}1000^{\circ}C$) 변화에 따른 입자 사이즈와 입도 분포를 측정하였다. 제조된 $BaTiO_3$분말의 결정 구조 분석을 위하여 XRD (X-ray diffraction) 분석을 수행 하였는데, 분석 결과로부터 제조된 분말들이 정방정 (tetragonal)의 perovskite구조를 갖고 있음을 확인하였다. 또한 분말의 미세구조 확인을 위하여 SEM (scanning electron microscope) 관찰을 수행하였는데, 나노 사이즈의 구형 분말을 얻을 수 있음을 확인할 수 있었다.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.3
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• pp.243-251
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• 2018

In this study, we compared the MZVI (Microscale Zero-Valent Iron) and NZVI (Nanoscale Zero-Valent Iron) for reactivity and mobility in a column to reduce nitrate, which is a major pollutant in Korea, and investigated the effect of operational parameters on the NZVI filled column. For the comparison of MZVI and NZVI, samples were collected for 990 minutes using fractionator in the similar operation conditions (MZVI 10g, NZVI 2g). The nitrate reduction efficiency of NZVI was about 5 times higher than that of MZVI, which was about 7.45% and 38.75% when using MZVI and NZVI, respectively. In the mobility experiment, the MZVI descended due to gravity while NZVI moved up with water flow due to its small size. Furthermore, the optimum condition of NZVI filled column was determined by changing the flow rate and pH. The amount of Fe ions was increased as the pH of the nitrate solution was lowered, and the nitrate removal rate was similar due to the higher yield of hydroxyl groups. The removal rate of nitrate nitrogen was stable while flow rate was increased from 0.5 mL/min to 2.0 mL/min (empty bed contact time: 2.26 min to 0.57 min). NZVI has a high reduction rate of nitrate, but it also has a high mobility, so both of reactivity and mobility need to be considered when NZVI is applied for drinking water treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.219-220
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• 2013

The phenomenology of liquid breakdown has been an area of interest for many years but is still not fully understood. Moreover, it was known that the behavior of magnetic nanoparticles in transformer oil could affect the dielectric breakdown voltage positively or negatively. In this study, we have imaged the magnetic nanoparticles in a transformer oil in-situ using an optical microscopic set-up and a microchannel according to the electric and magnetic fields applied. And we have calculated numerically dielectrophoresis and magnetophoresis forces, which must be the driving mechanisms to move magnetic nanoparticles in the fluid. It was found that when the electric field is applied the magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field.