• Korean Chemical Engineering Research
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• 제46권4호
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• pp.727-731
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• 2008

계면활성제(P123)를 주형물질로 사용하여 메조포러스 구조의 Pt-Au 합금박막을 전기화학적 증착법에 의해 ITO가 코팅된 유리 위에 합성하였다. 전해질은 각각 10 mM의 $H_2PtCl_6$와 $HAuCl_4$의 혼합용액에 일정량의 계면활성제를 첨가하여 사용하였다. TEM(Transmission Electron Microscopy) 분석을 통하여 기공구조를 확인하였고, SEM(Scanning Electron Microscopy) 분석을 통하여 합성된 박막의 표면입자의 형태를 확인하였다. 합성된 메조포러스 구조의 Pt-Au 합금박막의 입자 함량비는 EDS(Energy Dispersive X-ray Spectroscopy) 분석으로 조사하였다. 메탄올 산화에 대한 전기화학적 촉매활성과 박막의 안정성을 평가한 결과 메조포러스 구조일 때, 넓은 표면적으로 인해 산화전류밀도가 월등히 증가함을 알 수 있었으며, 순수한 Pt박막과 비교하였을 때 소량의 Au입자의 첨가로 촉매적 안정성이 향상됨을 확인하였다.

• 한국재료학회지
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• 제9권12호
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• pp.1196-1204
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• 1999

(hfac)Cu(vtmos) [$C_{10}H_{13}O_{5}CuF_{6}$Si: 1,1,1,5,5,5-hexafluoro-2,4- pentadionato (vinyltrimethoxysilane) copper (I)] 구리원을 액체분사법으로 공급하여 반응성 스퍼터 증착된 PVD-TiN과 급속열처리 변환된 RTP-TiN 기판상에 구리를 유기금속 화학증착법으로 성장시키고, 증착조건과 기판 종류가 박막의 증착율, 결정구조 및 미세조직, 전기비저항 등에 미치는 영향을 분석하였다. 구리원 유량 0.2ccm에서 증착반응은 Ar 유량 200sccm까지 물질전달 지배과정과 전압 1.0Torr 이상에서 기화기에서의 공급율속을 보였다. 전압 0.6Torr일 때 활성화에너지는 155~225$^{\circ}C$의 표면반응 지배영역에서 12.7~14.1kcal/mol의 값을 나타내었으며, 225$^{\circ}C$ 이상의 기판온도에서는 $H_2$ 첨가에 따른 증착율 개선이 간응한 것으로 판단되었다. 증착층은 기판온도 증가에 따라 3차원 island 양식으로 성장하였으며, 증착초기 구리 핵생성밀도가 큰 RTP-TiN상 증착층이 PVD-TiN상보다 현저한 (111) 우선방위와 낮은 전기비저항값을 나타내었다. 구리박막의 전기비저항은 결정립간 연결성이 양호한 165$^{\circ}C$에서 가장 낮았으며, 증착온도에 따른 박막 미세구조 변화로 인해 그 거동은 3개의 영역으로 구분되어 나타났다.

• Corrosion Science and Technology
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• 제8권2호
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• pp.53-61
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• 2009

본 연구에서는 강교 도장재료로 사용될 수 있는 에폭시 하도 도료를 도포한 시험편을 촉진시험을 통해 열화시킨 후 도막의 외관 평가 및 EIS에 의한 평가를 실시하고, 그 2가지 방법에 대한 비교 분석을 실시하였다. 화상처리 기법에 의해 구한 총 열화 면적율과 열화도 평점 산정 결과를 상호 비교해 본 결과 녹이 발생한 경우가 그렇지 않은 경우보다 열화도 평점이 높게 나타났다. 이는 강교 도장의 열화도 평가 기준에서 단위 열화 면적율당 부여하는 열화도 평점이 박리의 경우보다 녹의 경우가 더 크기 때문이다. 열화 면적율과 EIS 측정 데이터를 비교해 본 결과 녹의 면적율 약 0.1% 이상, 블리스터링의 면적율 약 3% 이상만 되어도 도막의 임피던스는 약 $10^4{\Omega}{\cdot}cm^2$ 혹은 그 이하로 크게 저하되었다. 2개의 시험편을 제외한 모든 시험편에 대해 전하전달저항(charge transfer resistance, $R_{ct}$)과 이중층 정전용량(double layer capacitance, $C_{dl}$) 값이 나타났으며, 이 결과로부터 이들 시험편들은 도막과 강재 계면에 수분이 축적되어 부식이 진행되고 있음을 알 수 있었다. 열화도 평점과 EIS 측정결과를 상호 비교해 본 결과 저주파수(10 mHz)에서의 임피던스 값이 $10^6{\Omega}{\cdot}cm^2$ 이하로 떨어진 경우는 모두 열화도 평점이 10점 이상으로 나타났으며, NORSOK cyclic test 과정에 의해 열화시킨 경우 열화도 평점이 높지 않음에도 불구하고 임피던스는 가장 낮게 나타났다. 이것은 도장계와 열화조건이 주 시험편과 다르기 때문인 것으로 판단되며, 열화조건이 더 가혹하거나 복합적일 경우 외관 상태에 비해 도막의 저항이 더 크게 저하될 가능성이 있다고 생각된다.

• Journal of Biosystems Engineering
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• 제12권2호
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• pp.16-27
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• 1987

Greenhouse farming was introduced to the Korean farmers in the middle of 1950's and its area has been increased annually. The plastic greenhouse, which is covered with polyethylene or polyvinyl chloride film, has been rapidly spread in greenhouse farming since 1970. The greenhouse farming greatly contributed to the increase of farm household income and the improvement of crop productivity per unit area. Since the greenhouse farming is generally practiced during winter, from November to March, the thermal environment in the plastic greenhouse should be controlled in order to maintain favorable condition for plant growing. Main factors that influence the thermal environment in the plastic greenhouse are solar radiation, convective and radiative heat transfer among the thermal component of the greenhouse, and the use of heat source. The objective of this study was to develop a simulation model for thermal environment of the plastic greenhouse in order to determine the characteristics of heat flow and effects of various ambient environmental conditions upon thermal environments within the plastic greenhouse. The results obtained are summarized as follows: 1. Simulation model for thermal environment of the plastic greenhouse was developed, resulting in a good agreement between the experimental and predicted data. 2. Solar radiation being absorbed in the plant and soil during the daytime was 75 percent of the total solar radiation and the remainder was absorbed in the plastic cover. 3. About 83 percent of the total heat loss was due to convective and radiative heat transfer through the plastic cover. Air ventilation heat loss was 5 to 6 percent of total heat loss during the daytime and 16 to 17 percent during the night. 4. The effectiveness of thermal curtain for the plastic greenhouse at night was significantly increased by the increase of the inside air temperature of the greenhouse due to the supplementary heat. 5. When the temperature difference between the inside and outside of the greenhouse was small, the variation of ambient wind velocity did not greatly affect on the inside air temperature. 6. The more solar radiation in the plastic greenhouse was, the higher the inside air temperature. Because of low heat storage capacity of the plant and soil inside the greenhouse and a relatively high convective heat loss through the plastic cover, the increase of solar radiation during the daytime could not reduce the supplymentary heat requirement for the greenhouse during the night.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.87-87
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• 2010

Photoelectrochemical (PEC) systems are promising methods of producing H2 gas using solar energy in an aqueous solution. The photoelectrochemical properties of numerous metal oxides have been studied. Among them, the PEC systems based on TiO2 have been extensively studied. However, the drawback of a PEC system with TiO2 is that only ultraviolet (UV) light can be absorbed because of its large band gap (3.2 - 3.4 eV). Two approaches have been introduced in order to use PEC cells in the visible light region. The first method includes doping impurities, such as nitrogen, into TiO2, and this technique has been extensively studied in an attempt to narrow the band gap. In comparison, research on the second method, which includes visible light water splitting in molecular photosystems, has been slow. Mallouk et al. recently developed electrochemical water-splitting cells using the Ru(II) complex as the visible light photosensitizer. the dye-sensitized PEC cell consisted of a dye-sensitized TiO2 layer, a Pt counter electrode, and an aqueous solution between them. Under a visible light (< 3 eV) illumination, only the dye molecule absorbed the light and became excited because TiO2 had the wide band gap. The light absorption of the dye was followed by the transfer of an electron from the excited state (S*) of the dye to the conduction band (CB) of TiO2 and its subsequent transfer to the transparent conducting oxide (TCO). The electrons moved through the wire to the Pt, where the water reduction (or H2 evolution) occurred. The oxidized dye molecules caused the water oxidation because their HOMO level was below the H2O/O2 level. Organic dyes have been developed as metal-free alternatives to the Ru(II) complexes because of their tunable optical and electronic properties and low-cost manufacturing. Recently, organic dye molecules containing multi-branched, multi-anchoring groups have received a great deal of interest. In this work, tri-branched tri-anchoring organic dyes (Dye 2) were designed and applied to visible light water-splitting cells based on dye-sensitized TiO2 electrodes. Dye 2 had a molecular structure containing one donor (D) and three acceptor (A) groups, and each ended with an anchoring functionality. In comparison, mono-anchoring dyes (Dye 1) were also synthesized. The PEC response of the Dye 2-sensitized TiO2 film was much better than the Dye 1-sensitized or unsensitized TiO2 films.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.475-480
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• 2017

본 논문에서는 레이저 유도증착 공정을 사용하여 절연기판위에 미세패턴의 전도성 향상시켰다. 기존의 레이저 유도증착의 공정에서 발생하는 높은 레이저빔 에너지로 인하여, 미세패턴의 낮은 증착밀도, 산화와 같은 문제점이 있다. 이러한 문제점을 폴리머 코팅층을 사용하여 증착정밀도와 전도성 향상하였다. 실리콘 웨이퍼 위에 미세패턴 증착을 위해서 크롬, 구리를 사용하였다. 본 연구에서는 다중펄스 방식의 레이저 빔을 금속박막에 조사하여 절연기판(insulating substrate: $SiO_2$) 위에 시드 층을 형성하고, 형성된 시드 층위에 무전해 도금을 적용하여 미세패턴 및 구조물을 제작하는 복합공정기술을 개발하였다. 레이저빔의 다중 스캔방식으로 조사함으로서 레이저빔의 에너지가 증착 층의 증착밀도와 표면품위를 향상시키고, 미세전극 패턴으로 사용가능한 전기 전도성을 갖게 되었음 알 수 있었다. 레이저 직접묘화법과 무전해 도금을 적용한 복합공정을 이용하여 미세전극을 증착 한 후 비저항을 측정한 결과 도금 전 저항이 $6.4{\Omega}$, 도금 후의 저항이 $2.6{\Omega}$으로 미세전극 패턴의 표면조직이 균일하고 증착되었다. 표면조직이 균일하고 치밀하게 증착되었기 때문에 전기 전도도가 약 3배정도 향상되었다.

• 한국자기학회지
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• 제26권6호
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• pp.179-184
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• 2016

스핀전달토크(Spin-Transfer Torque: STT) MRAM의 상용화를 위해서는 낮은 반전전류와 높은 열적 안정성을 동시에 만족해야 하고, 이를 위해서는 큰 스핀 분극, 강한 수직자기이방성 에너지을 가지는 물질이 요구된다. 본 연구에서는 STT-MRAM에 적합한 물질로 알려진 B2 CoFe 면심에 X(O, F, S, Cl) 원자가 위치한 $CoFeX_3$ 합금의 전자구조와 자기결정이방성(Magnetocrystalline anisotropy: MCA) 에너지를 계산하였다. X 원자가 F나 Cl일 때는 페르미 준위에서의 스핀 분극율이 각각 97 %, 96 %로, 반쪽 금속에 근접한 전자구조를 가짐을 확인할 수 있었다. 뿐만 아니라 표면이 Co 원자로 끝나는 5층 박막은 모든 X에 대해 수직 자기이방성를 가졌으며, 특히 $CoFeCl_3$의 자기이방성 에너지는 약 1.0 meV/cell로 상당히 컸다. 따라서 6, 7 족 원소를 잘 활용하면 높은 스핀 분극율과 강한 수직 자기이방성를 동시에 가지는 물질을 제조할 수 있게 되어 STT-MRAM의 상용화에 기여를 할 수 있을 것으로 기대한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• 한국인쇄학회지
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• 제30권3호
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• pp.45-56
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• 2012

Printing technology is accepted by appropriate technology that smart phones, tablet PC, display(LCD, OLED, etc.) precision recently in the electronics industry, the market grows, this process in the ongoing efforts to improve competitiveness through the development of innovative technologies. So printed electronics appeared by new concept. This technology development is applied on electronic components and circuits for the simplification of the production process and reduce processing costs. Low-temperature process making possible for widening, slimmer, lighter, and more flexible, plastic substrates, such as(flexible) easily by forming a thin film on a substrate has been studied. In the past, the formation of the electrode used a screen printing method. But the screen printing method is formation of fine patterns, high-speed printing, mass production is difficult. The roll-to-roll printing method as an alternative to screen printing to produce electronic devices by printing techniques that were used traditionally in the latest technology and processing techniques applied to precision control are very economical to implement fine-line printing equipment has been evaluated as. In order to function as electronic devices, especially the dozens of existing micro-level of non-dot print fine line printing is required, the line should not break at all, because according to the specifications required to fit the ink transfer conditions should be established. In this study of roll-to-roll printing conductive paste suitable for gravure offset printing by developing Ag paste for forming fine patterns to study the basic physical properties with the aim of this study were to.

• 전기학회논문지
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• 제67권3호
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• pp.413-418
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• 2018

In this paper, we describe the development of a non-enzymatic glucose sensor based on copper nanocubes(Cu NCs) electroplated laser induced graphene(LIG) electrodes which can detect a certain range of glucose concentrations. $CO_2$ laser equipment was used to form LIG electrodes on the PI film. This fabrication method allows easy control of the LIG electrode size and shape. The Cu NCs were electrochemically deposited on the LIG electrodes to improve electron transfer rates and thus enhancing electrocatalytic reaction with glucose. The average sheet resistances before and after electroplating were $15.6{\Omega}/{\Box}$ and $19.6{\Omega}/{\Box}$, respectively, which confirmed that copper nanocubes were formed on the laser induced graphene electrodes. The prepared electrode was used to measure the current according to glucose concentration using an electrochemical method. The LIG electrodes with Cu NCs demonstrated a high degree of sensitivity ($1643.31{\mu}A/mM{\cdot}cm^2$), good stability with a linear response to glucose ranging from 0.05 mM to 1 mM concentration, and a limit of detection of 0.05 mM. In order to verify that these electrodes can be used as flexible devices, the electrodes were bent to $30^{\circ}$, $90^{\circ}$, and $180^{\circ}$ and cyclic voltammetry measurements were taken while the electrodes were bent. The measured data showed that the peak voltage was almost constant at 0.42 V and the signal was stable even in the flexed condition. Therefore, it is concluded that these electrodes can be used in flexible sensors for detecting glucose in the physiological sample like saliva, tear or sweat.