• Korean Chemical Engineering Research
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• 제46권5호
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• pp.886-891
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• 2008

접촉 글로우방전 전기분해(CGDE)는 일반적인 전기분해와 다르게 높은 전압에서 전극과 전극을 둘러싼 전해질 사이에 글로우 방전에 의한 플라즈마가 형성돼 일어나는 전기분해다. 본 연구에서는 먼저 NaCl 용액에서 CGDE 거동을 파악하고 그리고 CGDE에 의한 후코이단의 저분자화에 대해 연구하였다. NaCl 전해질에서 CGDE 과정이 시작되면 전압 증가에 따라 글로우 방전이 활발하게 되고 그에 따라 전류밀도가 감소하고 온도가 내려갔다. 반응시간에 따른 후 코이단의 분자량 변화로부터 저분자화반응은 1차 반응속도 식을 따름을 보였다. CGDE에 의해 후코이단의 분자량이 처음의 약 1/40로 감소하였으며, CGDE 저분자화 과정에서 황산기 함량과 fucos 함량의 감소가 없었다.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3629-3633
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• 2011

The effect of a dense $TiO_2$ blocking layer prepared using the sol-gel method on the performance of dye-sensitized solar cells was studied. The blocking layer formed directly on the working electrode, separated it from the electrolyte, and prevented the back transfer of electrons from the electrode to the electrolyte. The dyesensitized solar cells were prepared with a working electrode of fluorine-doped tin oxide glass coated with a blocking layer of dense $TiO_2$, a dye-attached mesoporous $TiO_2$ film, and a nano-gel electrolyte, and a counter electrode of Pt-deposited FTO glass. The gel processing conditions and heat treatment temperature for blocking layer formation affected the morphology and performance of the cells, and their optimal values were determined. The introduction of the blocking layer increased the conversion efficiency of the cell by 7.37% for the cell without a blocking layer to 8.55% for the cell with a dense $TiO_2$ blocking layer, under standard illumination conditions. The short-circuit current density ($J_{sc}$) and open-circuit voltage ($V_{oc}$) also were increased by the addition of a dense $TiO_2$ blocking layer.

• 대한기계학회논문집B
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• 제39권5호
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• pp.397-403
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• 2015

본 연구는 고분자 전해질 연료전지 (PEMFC)의 성능에 매우 중요한 영향을 미치는 물의 분포를 실험적으로 측정하였다. 내부에서 일어나는 활발한 화학반응과 물질전달 특성 때문에 PEMFC 내부에서 수분의 분포가 불균일하며 그 분포를 실험적으로 측정하기가 용이하지 않아 그 동안 간접적인 측정이 많이 이루어졌다. 본 연구에서는 초소형 온습도 센서를 연료전지의 채널에 직접 삽입하고 채널을 따라 흐르는 반응가스의 습도를 측정하였다. 수소극과 공기극 중 한곳만 가습하며, 가습하지 않은 곳에서 습도를 측정하여 멤브레인을 통한 물의 이동을 연구하였다. 가습기의 온도가 증가할수록 양극의 물농도 구배가 커져서 확산이 증가하나 높은 전류밀도에서는 전기삼투항력의 영향이 더욱 커졌다.

• 수산해양교육연구
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• 제28권5호
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• pp.1444-1458
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• 2016

The expansion of high-density aquaculture in the limited waters has caused a wide variety of problems. The problems include environmental problems nearby aquaculture sites, growth rate of aquatic organisms, quality decline of farmed fish and price fall in the market. The phenomenon of aquaculture industry happens in not only inshore but also offshore. Therefore, the fisheries authorities have been changing their policy paradigms from mass production to sustainable production based on ecosystem. Other countries, however, focusing on relieving poverty and providing protein from fish production have not recognized the degree of seriousness. When it comes to enhancing the problems, National Institute of Fisheries Science has been developing the technology of Integrated Multi-Trophic Aquaculture (IMTA) to reduce and to prevent contaminants from fish and aquaculture sites, remained feed from fish farming process. In long-terms of view, the system is one of the most sustainable fishery production methods based on ecosystem. As integration of nutrient feed system from aquatic organisms is firmly established, the earlier mentioned problems will be diminished gradually. In term of the substantiality, this study was conducted. The research on management system for IMTA also has been incorporated. This study also investigated the features and current status of IMTA and demonstrated the developed management system and direction for the future advancement.

• 반도체디스플레이기술학회지
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• 제4권2호
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• pp.15-19
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• 2005

The organic light-emitting devices(OLEDs) based on fluorescence have low efficiency due to the requirement of spin-symmetry conservation. By using the phosphorescent material, the internal quantum efficiency can reach 100$\%$, compared to 25$\%$ in case of the fluorescent material [1]. Thus recently phosphorescent OLEDs have been extensively studied and showed higher internal quantum efficiency than conventional OLEDs. In this study, we have applied a new Ir complex as a red dopant and fabricated a red phosphorescent OLED on a flexible PC(Polycarbonate) substrate. Also, we have investigated the electrical and optical properties of the devices with a structure of A1/LiF/Alq3/(RD05 doped)BAlq/NPB/2-TNAIA/ITO/PC substrate. Our device showed the lightening efficiency of > 30 cd/A at an initial brightness of 1000 cd/$m^{2}$. The CIE(Commission Internationale de L'Eclairage) coordinates for the device were (0.62,0.37) at a current density of 1 mA/$cm^{2}$. In addition, although the sheet resistance of ITO films on PC substrate is higher than that on glass substrate, the flexible OLED showed much better lightening efficiency without much increase in operating voltage.

• 반도체디스플레이기술학회지
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• 제10권3호
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• pp.67-74
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• 2011

In this study, we have investigated the effect of the substrate temperature on the structural and the electrical characteristics of IZO thin films for the OLED (organic light emitting diodes) devices. For this purpose, IZO thin films were deposited by RF magnetron sputtering under various substrate temperature. The substrate temperature has been changed from room temperature to $400^{\circ}C$. Samples which were deposited under $250^{\circ}C$ show amorphous structure. The electrical resistivity of crystalline-IZO (c-IZO) film was higher than that of amorphous-IZO (a-IZO) film. And the electrical resistivity showed minimum value near $150^{\circ}C$ of deposition temperature. The OLED device was fabricated with different IZO substrates made by configuration of IZO/$\acute{a}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show better current density-voltage-luminance characteristics than that of OLED devices with the commercial crystalline-ITO (c-ITO) anode film. It can be explained that very flat surface roughness and high work function of a-IZO anode film lead to more efficient hole injection by reduction of interface barrier height between anode and organic layers. This suggests that a-IZO film is a promising anode materials substituting conventional c-ITO anode in OLED devices.

• 전기전자학회논문지
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• 제15권4호
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• pp.324-329
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• 2011

휴대 기기가 고기능화, 다기능화 됨에 따라 다양한 멀티미디어 기능이 요구되면서 배터리를 보다 장시간 이용하면서 더 높은 전력과 에너지가 요구되고 있다. 이에 따라 여러 개의 리튬이온 cell을 연결한 배터리팩이 많이 사용되고 있다. 2개 이상의 cell로 구성된 리튬이온 배터리를 안전하게 사용하기 위해서는 과전압 및 과전류, 고온으로 부터 보호해야 됨은 물론, 수명을 연장하기 위해서 각 cell의 전압을 같게 유지시켜주는 balancing 기능이 반드시 요구된다. 본 논문에서 제안한 IC는 모바일 기기뿐만 아니라 E-bike, 하이브리드 자동차, 전기 자동차 분야에도 적용 가능할 것으로 예상되며, 국내 PMIC 발전에 기여할 것으로 기대된다.

• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.39-44
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• 2011

In this study, we have investigated the structural and electrical characteristics of IZO thin films deposited on flexible substrate for the OLED (organic light emitting diodes) devices. For this purpose, PES was used for flexible substrate and IZO thin films were deposited by RF magnetron sputtering under oxygen ambient gases (Ar, $Ar+O_2$) at room temperature. In order to investigate the influences of the oxygen, the flow rate of oxygen in argon mixing gas has been changed from 0.1sccm to 0.5sccm. All the samples show amorphous structure regardless of flow rate. The electrical resistivity of IZO films increased with increasing flow rate of $O_2$ under $Ar+O_2$. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO electrodes made by configuration of IZO/a-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show better current density-voltage-luminance characteristics than that of OLED devices with the commercial crystalline-ITO (c-ITO) anode film. It can be explained that very flat surface roughness and high work function of a-IZO anode film lead to more efficient hole injection by reduction of interface barrier height between anode and organic layers. This suggests that a-IZO film is a promising anode materials substituting conventional c-ITO anode in OLED devices.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.373-379
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• 2002

We investigated the evolution of magnetoresistance and magnetic property of tunneling magnetoresistive(TMR) device with microstructure and plasma oxidation time. TMR devices have potential applications for non volatile MRAM and high density HDD reading head. We prepared the tunnel magnetoresistance(TMR) devices of Ta($50{\AA}$)/NiFe($50{\AA}$)/IrMn($150{\AA}$)/CoFe($50{\AA}$)/Al($13{\AA}$)-O/CoFe($40{\AA}$)/FiFe($400{\AA}$)/Ta(($50{\AA}$) structure which have $100{\times}100\mu\textrm{m}^2$ junction area on $2.5{\times}2.5\textrm{cm}^2$ Si/$SiO_2$(($1000{\AA}$) substrates by an inductively coupled plasma(ICP) magnetron sputter. We fabricated the insulating layer using an ICP plasma oxidation method by with various oxidation time from 30 sec to 360 sec, and measured resistances and magnetoresistance(MR) ratios of TMR devices. We found that the oxidized sample for oxidation time of 80 sec showed the highest MR radio of 30.31 %, while the calculated value regarding inhomogeneous current effect indicated 25.18 %. We used transmission electron microscope(TEM) to investigate microstructural evolution of insulating layer. Comparing the cross-sectional TEM images at oxidation time of 150 sec and 360 sec, we found that the thickness and thickness variation of 360 sec-oxidized insulating layer became 30% and 40% larger than those of 150 sec-oxidized layer, repectively. Therefore, our results imply that increase of thickness variation with oxidation time may be one of the major treasons of the MR decrease.

• 전기화학회지
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• 제18권4호
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.