• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1347-1348
• /
• 2007

In this paper, ITO gate electrode surface was modified using $O_2$ plasma and organic gate insulating layers were deposited on the ITO surface using plasma polymerization technique. In order to investigate the influence of the plasma coupling method and plasma conditions on the plasma polymerized methyl methacrylate (ppMMA) thin film properties, inductively coupled (ICP) and capacitively coupled plasma (CCP) were used to generate the plasma and the plasma parameters were varied. The ppMMAs were investigated using atomic force microscopy (AFM) and a Fourier Transform Infrared (FT-IR) spectroscopy. Dielectric constants of the ppMMA thin films were investigated using a impedance analyzer (HP4192A, LF Impedance Analyzer). Current-Voltage (I-V) characteristics of the organic thin film transistors (OTFTs) were investigated using a source measurement unit (SMU: Keithley 2612). Proposed method can be applied to dry-process to fabricate OTFTs during overall fabricating steps.

• 전기화학회지
• /
• 제3권2호
• /
• pp.121-126
• /
• 2000

[ $AB_5$ ] 수소저장합금인 $LaNi_5$, 합금분말에 Ni 및 Cu 무전해 도금의 영향을 전기 화학적 실험을 통하여 고찰하였다. 전기 화학적 실험은 정전류 충$\cdot$방전 실험, 순환전류전위 실험, 교류 임피던스 실험 등을 실시하여 도금하지 않은 $LaNi_5$ 전극과 Ni 및 Cu 무전해 도금한 전극간의 특성을 비교 연구하였다. 현상학적인 분석으로는 SEM을 이용하여 분말상의 미세조직을 관찰하였으며 X-선 회절시험을 실시하였다 무전해 도금을 실시하여 Ni 및 Cu박막이 피복된 수소저장 합금은 활성화 특성파 싸이클 수명 등의 특성이 개선되었으며 도금하지 않은 전극에 비하여 반응속도가 증가하였다. 또한 충$\cdot$방전이 반복됨에 따라 전극과 전해질 계면에서의 전하이동저항이 현저하게 감소하였다. 따라서 본 연구에서 실시한 $LaNi_5$, 활물질에 Ni및 Cu 무전해 도금을 실시하면 초기 활성화반응을 촉진시키며 $LaNi_5$활물질이 전해질과의 직접 접촉을 피하게 되어 전극의 수명을 증가시키는 것을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
• /
• pp.396-401
• /
• 1995

Epoxy coated reinforcing steels (ECRs) were acquired from ten sources and coatings from each source were initially characterized in terms of defects, thickness, solvent extraction weight loss and hardness. Testing involved exposure in three aqueous solutions at elevated temperature (8$0^{\circ}C$) and in chloride-contaminated concrete slabs under outdoor exposure, It was found that the density and size of coating defects was the promary factor affecting ECR performance. The equivalent circuit analysis using electrochemical impedance spectroscopy (EIS) data indicated that the impedance response for well-performing ECR specimens showed no signs of active degradation at the interface although diffusional processes similar to those noted for poorly performing bars occurred here. Experimental results also indicated a relationship between corrosion behavior and bar source. Weight loss upon solvent extraction correlated with impedance reduction from hot water exposure. Coating defects during most of the tests, especially in high pH solutions containing chloride ions. ECRs with excessive coating defects, either initially present or ones which developed in service, performed poorly in every test category regardless of source. Forms of coating failure were extensive rusting at defects, blistering, wet adhesion loss, cathodic delamination, underfilm corrosion and coating cracks. These occurred sequentially or concurrently, depending on the condition of the ECR and nature of the environment

• 한국세라믹학회지
• /
• 제35권10호
• /
• pp.1070-1077
• /
• 1998

Effect of current collecting layer on the cathode was characterized by AC impedance spectroscopy at 800$^{\circ}C$ under flowing air. LSM-YSZ composite cathode showed lower polarization resistance due to the in-crease of triple phase (LSM/YSZ/Pore) boundary length by incorporation of YSZ. Ohmic resistance {{{{ {R }_{1 } }} of LSM-YSZ was higher than that of pure LSM however because in-plane resistance of the cathode was fair-ly high due to its high specific resistivity. To reduce the in-plane resistance of LSM-YSZ cathode cathode side current collecting layer was required. Ohmic resistance {{{{ {R }_{1 } }} was reduced after forming LSM current col-lecting layer on the LSM-YSZ cathode. In case of pure LSM cathode the formation of Pt, or LSCO current collecting layer reduced polarization resistance {{{{ {R }_{p } }} but ohmic resistance {{{{ {R }_{1 } }} was relatively constant. After annealing of LSM cathode with Pt current collector at higher temperature polarization resistance {{{{ {R }_{p } }} was in-creased but ohmic resistance {{{{ {R }_{1 } }} was constant. These phenomena indicate that Pt or LSCo current col-lecting layers act as a catalytic layer for oxygen reduction of pure LSM cathode. LSCO current collector was effective in reducing the ohmic and polarization resistance of LSM-YSZ cathode.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.277-278
• /
• 2005

Admittance Spectroscopic analysis was applied to study the effect of LiF buffer layer and to model the equivalent circuit for poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymer light emitting diodes (PLEDs) with the LiF cathode buffer layer. The single layer device with ITO/MEH-PPV/Al structure can be modeled as a simple parallel combination of resistor and capacitor. Insertion of a LiF layer at the Al/MEH-PPV interface shifts the highest occupied molecular orbital level and the vacuum level of the MEH-PPV layer as a result the barrier height for electron injection at the Al/MEH-PPV interface is reduced. The admittance spectroscopy measurement of the devices with the LiF cathode buffer layer shows reduction in contact resistance ($R_c$), parallel resistance ($R_p$) and increment in parallel capacitance ($C_p$).

• Journal of Electrochemical Science and Technology
• /
• 제14권4호
• /
• pp.311-319
• /
• 2023

This work was performed to characterize the electrochemical behavior of AZ31 Mg alloy in neutral aqueous solutions where Cl^-, SO₄^2-, PO₄^3-, and F^- ions were present and pH was adjusted to 6 to exclude the contribution of H⁺ and OH^- ions. Open-circuit potential (OCP) transient, electrochemical impedance spectroscopy (EIS) and potnetiodynamic polarization curves were employed. The OCP value appeared to decrease in the order of F^- > Cl^- > SO₄^2- > PO₄^3- ions while corrosion current density increased in the same order. Electrochemical impedance spectroscopy (EIS) data showed two capacitive arcs in all the solutions and one more inductive arc appeared in PO₄^3--containing solution. By fitting of two capacitive arcs, capacitance of dense film (C_df), resistance of porous film (R_pf) and double layer capacitance (C_dl) and charge transfer resistance (R_ct) beneath the porous films were obtained. A simplified model in which various thicknesses and coverages of dense and porous films are assumed to be present on the AZ31 Mg alloy surface, is suggested to explain the effects of four different anions on the electrochemical behavior of AZ31 Mg alloy.

• 한국세라믹학회지
• /
• 제36권2호
• /
• pp.130-135
• /
• 1999

고로슬래그 시멘트의 저온 조기 강도를 증진키 위하여 고로슬래그의 분말도를 높이고 낮은 물:시멘트 비(W/C)의 혼합수량을 사용하였다. 분쇄조제를 사용하여 6,280$\textrm{cm}^2$/g(Blaine)로 미분쇄한 고로슬래그를 일반 포틀랜드 시멘트와 혼합하여 고로슬래그 40%의 고로슬래그 시멘트를 만들었다. 그리고 시판의 naphthalene계 고성능감수제를 사용하여 혼합수량을 W/C=0.50(KS L 5105)에서 W/C=0.33으로 저하시킬 수 있었다. 상술한 방법을 통하여 고로슬래그 시멘트의 저온 조기 강도를 포트랜드 시멘트 강도보다 오히려 더 높게 향상시킬 수 있었으며, 기공구조 및 임피던스 분석의 방법으로 본 시멘트의 미세구조를 조사하였다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 봄 학술논문 발표대회
• /
• pp.57-58
• /
• 2022

Reinforced concrete (RC) structures play a significant role in the construction industries. An embeddable solid-state reference electrode (ESSRE) was used to evaluate the corrosion status of steel rebar in the concrete of various cover thicknesses that exposed to the maritime environment (3.5 % NaCl) in this study. From the open circuit potential measurement (OCP), the passive state, the corrosion uncertainty, and the 90% probability of corrosion state of the steel rebars in the concrete were monitored by ESSRE. From the electrochemical impedance spectroscopy (EIS) method, severe corrosion was observed at the exposure period of 1510, 1847, 2350, and 3020 h for C10, C15, C20, and C30 concrete, respectively. The results confirm that the ESSRE can be useful to identify the corrosion occurrence and severe corrosion of steel rebar embedded in different cover depth concrete structures.

• Applied Microscopy
• /
• 제47권3호
• /
• pp.121-125
• /
• 2017

This study deals the prediction of temperature effect on low-frequency dispersion of alternating current (AC) conductivity spectra of composite materials based on copolymer reinforced with carbon black (CB) particles. A sample of ethylene butylacrylate loaded with 13% of CB particles were prepared and investigated using the impedance spectroscopy representation in the frequency range from 40 Hz to 0.1 MHz and temperature range from $20^{\circ}C$ to $125^{\circ}C$. The dielectric constant, ${\varepsilon}^{\prime}$, and dielectric losses, ${\varepsilon}^{{\prime}{\prime}}$, were found to decrease with increasing frequency. The frequency dependence of the AC conductivity follows the universal power law with a large deviation in the high frequency region, the positive temperature coefficient in resistivity effect has been observed below the melting temperature which makes this composite potentially remarkable for industrial applications.

• 한국세라믹학회지
• /
• 제44권12호
• /
• pp.715-719
• /
• 2007

STS444 with or without $La_{0.9}Sr_{0.1}MnO_3$ (LSM)-coating was contacted to $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) cathode on various electrolyte materials and the polarization resistance $(R_p)$ was measured by impedance spectroscopy. By making a symmetric half-cell and contacting only one side of the cathode with the interconnect, the effect of chromium (Cr) poisoning was separated from the aging effects. When the LSCF cathode was contacted with LSM-coated STS (stainless steel), $R_p$ of LSCF was lower than that contacted with the uncoated STS. Impedance patterns measured for the working electrode (W.E.), the counter electrode (C.E.) at $600^{\circ}C$ in air were analyzed. Normalized data of net Cr effect showed that $Ce_{0.9}Gd_{0.1}O_2$ (GDC) electrolyte is more tolerant to the chromium poisoning than $La_{0.9}Sr_{0.1}Ga_{0.8}Mg_{0.2}$ (LSGM) or 8 mol% $Y_2O_3-doped$ $ZrO_2$ (YSZ) electrolytes.