• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.308-308
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• 2013

본 연구에 염료감응형 태양전지(Dye Sensitized Solar Cells; DSSCs)의 광전변환효율을 높이기 위해 작업전극에 새로운 구조의 광투과층 및 산란층을 도입하였다. DSSCs 작업전극의 빛을 투과시키는 투과층에 크기가 10 nm 이하의 nanoparticle $TiO_2$를 적용하고, 투과된 빛이 산란되어 많은 전자가 여기 될 수 있도록 기존의 큰 입자 사이즈였던 산란층을 이용하는 대신 $TiO_2$ nanorod 및 nanotube 형태의 구조를 도입하여 기존의 작업전극과 비교하였다. 산란층에서 방향성을 가지는 rutile 상의 $TiO_2$는 저온에서 안정적인 anatase 상의 $TiO_2$보다 화학적으로 안정하며, 높은 산란율을 가지고, 광에 의해 여기된 전자를 직접적으로 집전전극에 전달해 줌으로서 소자의 효율을 증가시킨다고 보고되고 있다. Rutile 상의 $TiO_2$ 층 제작 시 수열합성법을 이용하면 nanorod 모양의 $TiO_2$층을 형성할 수 있고, 이와 같은 방법으로 성장시킨 산란층에 전기영동법의 식각 효과를 사용하면 nanotube 모양의 $TiO_2$층을 성장시킬 수 있어 산란효과의 극대화 및 전극의 표면적을 넓히는 장점이 있다. 각각의 방법을 이용하여 만든 구조 위에 입자 크기 10 nm의 $TiO_2$를 Dr blade 방법으로 도포하여 double layer (산란층+흡수층)로 구성된 작업 전극을 이용한 DSSCs를 제작한 후 I-V curve와 EIS (Electrochemical Impedance Spectroscopy)를 측정하여 효율 및 전기화학적 특성을 분석하였다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.2
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• pp.1-6
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• 2009

Nuclear power plants (NPP) using Alloy 600 (Ni 75wt%, Cr 15wt%, Fe 10wt%) as a heat exchanger tube of the steam generator (SG) have experienced various corrosion problems by ageing such as pitting, intergranular attack (IGA) and stress corrosion cracking (SCC). In spite of much effort to reduce the material degradations, SCC is still one of important problems to overcome. Especially lead is known to be one of the most deleterious species in the secondary system that cause SCC of the alloy. Even Alloy 690 (Ni 60wt%, Cr 30wt%, Fe 10wt%) as an alternative of Alloy 600 because of outstanding superiority to SCC is also susceptible to leaded environment. An oxide on SG tubing materials such as Alloy 600 and Alloy 690 is formed and modified expanding to complex sludge throughout hideout return (HOR) of various impurities including Pb. Oxide formation and breakdown is requisite for SCC initiation and propagation. Therefore it is expected that an oxide property such as a passivity of an oxide formed on steam generator tubing materials is deeply related to PbSCC and an inhibitor to hinder oxide modification by lead efficiently can be found. In the present work, the SCC susceptibility obtained by using a slow strain rate test (SSRT) in aqueous solutions with and without lead was discussed in view of the oxide property. The oxides formed on Alloy 600 and Alloy 690 in aqueous solutions with and without lead were examined by using a transmission electron microscopy (TEM), an energy dispersive x-ray spectroscopy (EDXS), an x-ray photoelectron spectroscopy (XPS) and an electrochemical impedance spectroscopy (EIS).

• Environmental Engineering Research
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• v.15 no.2
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• pp.71-78
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• 2010

To understand the effects of acclimation schemes on the formation of anode biofilms, different electrical performances are characterized in this study, with the roles of suspended and attached bacteria in single-chamber microbial fuel cells (MFCs). The results show that the generation of current in single-chamber MFCs is significantly affected by the development of a biofilm matrix on the anode surface containing abundant immobilized microorganisms. The long-term operation with suspended microorganisms was demonstrated to form a dense biofilm matrix that was able to reduce the activation loss in MFCs. Also, a Pt-coated anode was not favorable for the initial or long-term bacterial attachment due to its high hydrophobicity (contact angle = $124^{\circ}$), which promotes easy detachment of the biofilm from the anode surface. Maximum power ($655.0\;mW/m^2$) was obtained at a current density of $3,358.8\;mA/m^2$ in the MFCs with longer acclimation periods. It was found that a dense biofilm was able to enhance the charge transfer rates due to the complex development of a biofilm matrix anchoring the electrochemically active microorganisms together on the anode surface. Among the major components of the extracellular polymeric substance, carbohydrates ($85.7\;mg/m^2_{anode}$) and proteins ($81.0\;mg/m^2_{anode}$) in the dense anode biofilm accounted for 17 and 19%, respectively, which are greater than those in the sparse anode biofilm.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.311-315
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• 2010

The effects of $SO_2$ on the performance of proton exchange membrane(PEMFC) were investigated by introduction air containing $SO_2$ into cathode inlet of PEMFC. And the recovery of the cell performance by applying clean air, cycle voltammetry(CV) and high voltage holding following exposure contaminated air was studied. The $SO_2$ concentration range used in the experiments was from 20 ppb to 1.3 ppm. The performance degradation and recovery were measured by constant-current discharging, I-V polarization and electrochemical impedance spectroscopy(EIS). The cell voltage gradually decayed with time and decreased by 17 mV after 200 hours of 20 ppb $SO_2$ injection. The cell performance can be recovered partially by clean air flushing, CV and high voltage holding due to desorption of S from Pt catalyst.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.33.2-33.2
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• 2011

CMP (Chemical-Mechanical Planarization) 공정이란 화학적 반응과 기계적 힘을 동시에 이용하여 표면을 평탄화하는 공정으로, 반도체 산업에서 회로의 고집적화와 다층구조를 형성하기 위해 CMP 공정이 도입되었으며 반도체 패턴의 미세화와 다층화에 따라 CMP 공정의 중요성은 더욱 강조되고 있다. CMP 공정은 압력, 속도 등의 공정조건과, 화학적 반응을 유도하는 슬러리, 기계적 힘을 위한 패드 등에 의해 복합적으로 영향을 받는다. CMP 공정에서, 폴리우레탄 패드는 많은 기공들을 포함한 그루브(groove)를 형성하고 있어 웨이퍼와 직접적으로 접촉을 하며 공정 중 유입된 슬러리가 효과적으로 연마를 할 수 있도록 도와주는 역할을 한다. 하지만, 공정이 진행 될수록 그루브는 손상이 되어 제 역할을 하지 못하게 된다. 패드 컨디셔닝이란 컨디셔너가 CMP 공정 중에 지속적으로 패드 표면을 연마하여 패드의 손상된 부분을 제거하고 새로운 표면을 노출시켜 패드의 상태를 일정하게 유지시키는 것을 말한다. 한편, 금속박막의 CMP 공정에 사용되는 슬러리는 금속박막과 산화반응을 하기 위하여 산화제를 포함하는데, 산화제는 금속 컨디셔너 표면을 산화시켜 부식을 야기한다. 컨디셔너의 표면부식은 반도체 수율에 직접적인 영향을 줄 수 있는 scratch 등을 발생시킬 뿐만 아니라, 컨디셔너의 수명도 저하시키게 되므로 이를 방지하기 위한 노력이 매우 중요하다. 본 연구에서는 컨디셔너 표면에 연마 잔여물 흡착을 억제하고, 슬러리와 컨디셔너 표면 간에 일어나는 표면부식을 방지하기 위하여 소수성 자기조립 단분자막(SAM: Self-assembled monolayer)을 증착하여 특성을 평가하였다. SAM은 2가지 전구체(FOTS, Dodecanethiol를 사용하여 Vapor SAM 방법으로 증착하였고, 접촉각 측정을 통하여 단분자막의 증착 여부를 평가하였다. 또한 표면부식 특성은 Potentiodynamic polarization와 Electrochemical Impedance Spectroscopy (EIS) 등의 전기화학 분석법을 사용하여 평가되었다. SAM 표면은 정접촉각 측정기(Phoenix 300, SEO)를 사용하여 $90^{\circ}$ 이상의 소수성 접촉각으로써 증착여부를 확인하였다. 또한, 표면에너지 감소로 인하여 슬러리 내의 연마입자 및 연마잔여물 흡착이 감소하는 것을 확인 하였다. Potentiodynamic polarization과 EIS의 결과 분석으로부터 SAM이 증착된 표면의 부식전위와 부식전류밀도가 감소하며, 임피던스 값이 증가하는 것을 확인하였다. 본 연구에서는 컨디셔너 표면에 SAM을 증착 하였고, CMP 공정 중 발생하는 오염물의 흡착을 감소시킴으로써 CMP 연마 효율을 증가하는 동시에 컨디셔너 금속표면의 부식을 방지함으로써 내구성이 증가될 수 있음을 확인 하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.217-222
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• 2018

The deterioration of the Battery is decided by SoC and SoH. To determine Battery deterioration, SoC measurement method of Battery by Transfer Function was studied. The SoC of the Battery changes most greatly in the 1Hz band where the DC resistance is detected. but it is a narrow band to observe, therefore, the observation band was moved to 1kHz using the tone busrst signal. Welch's method was used to observe the frequency domain characteristics of the signal. As a result of the spectral estimation, it was confirmed that the response signal of the battery is 1dB difference when the SoC is 40%, 60%, and 80%, respectively. Through this, Proposed the new method of Battery SoC measurement.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.41-45
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• 2007

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4$-C/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4$-C/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/Li cell.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.247-252
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• 2013

Sulfonated poly(ether ether ketone) (SPEEK) with a certain degree of sulfonation were synthesized by reacting PEEK and sulfuric acid at different reaction time. Then ion-selective composite carbon electrodes (ISCCE) were fabricated by coating the prepared SPEEK on the surface of carbon electrodes. The specific capacitance and resistance of the ISCCE were analyzed by electrical impedance spectroscopy. The ion exchange capacities (IEC) of the SPEEKs were measured in the range of 1.60~2.57 meq/g depending on the sulfonation time. The SPEEK more than 2.5 meq/g of IEC was considered unsuitable for fabricating the ISCCE because it was dissolved in water. The specific capacitance of the prepared ISCCE increased with increasing the IEC of coated SPEEKs and the capacitance was improved up to about 20% compared to that of uncoated carbon electrode. In addition, the electrical resistance of coating layer decreased significantly with increasing the IEC of coated SPEEKs. It is expected that the desalination efficiency of conventional capacitive deionization process can be improved by using the prepared ISCCE coated with SPEEK.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.2
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• pp.142-149
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• 2013

Carbon materials are mainly used as catalyst supports for polymer exchange membrane fuel cell (PEMFC). Catalyst supports are required specific characteristics of the carbon materials, such as large surface area and high electrical conductivity. Attempted were to improve electrical conductivity and to maintain high surface area of carbon materials using a microwave treatment. Microwave treatment, as a relatively new technique, takes short reaction time and reduce the consumption of the gases used for carbon treatment compared to a traditional heat treatment. Hybrid carbon (ACF/Graphene) as catalyst supports by microwave-irradiation method for PEMFC increase the cell performance because of increased electrical conductivity resulting in triple-phase contact and reduced the interfacial resistance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-Ray Diffraction (XRD) were employed to analyze carbon materials. The performance of microwave-treated carbon materials was evaluated by measuring current-voltage (I-V) characteristics and electrode impedance.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.386.2-386.2
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• 2014

본 연구에서는 바이오 센서 응용을 위해 그래핀을 전극으로 제작하여 그래핀 표면 결함준위에 따른 센서의 민감도를 전기화학 실험을 통해 관찰하였다. 그래핀은 니켈/구리촉매를 이용한 저 진공 화학 기상 증착 장비(Low-Pressure Chemical Vapor Deposition; LP-CVD)와 Photo-lithography로 제작한 것과 탄소 산화물을 환원시켜 만든 환원-그래핀, 두 가지를 사용하였다. 전기화학 실험에서 그래핀 전극 및 Silver/Silver chloride (Ag/AgCl), Fluorine doped Tin Oxide (FTO)은 작업 전극 및 기준 전극, 상대 전극으로 각각 사용하였고, 반응용액은 potassium hexacyanoferrate (III)를 농도를 다르게 하여 사용하였다. 그래핀의 표면 상태, 층수, 결함 정도 등 구조적인 특성은 원자력현미경(Atomic Force Microscopy; AFM), 주사 전자 현미경(Secondary Electron Microscopy; SEM)과 Raman spectroscopy를 각각 이용하여 확인하였고, 그래핀의 결함준위에 따른 반응면적 및 센서 감도 의존성을 전류모드-원자력현미경(Current-Atomic Force Microscopy; I-AFM)과 전기화학 임피던스 분광법(Electrochemical Impedance Spectroscopy; EIS)를 통해 그래핀 전극의 성능을 분석하고, 그래핀 결함 준위에 따른 센서 감도 의존성은 순환전위 분광법 (Cyclic Voltammetry; CV)를 이용하여 관찰하였다. 또한 농도가 다른 반응용액은 센서의 민감도를 관찰하는데 사용하였다. 결과적으로 LP-CVD로 성장한 그래핀과 환원-그래핀의 결함준위에 따른 센서의 성능을 비교 분석한 결과와 반응용액 농도에 따른 센서의 민감도 결과는 그래핀 바이오센서에 대한 응용 및 상용화를 앞당기는데 기여할 것으로 예상한다.