• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.664-671
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• 1998

Poly pyrrole polymer(ppy) has an excellent electrical conductivity and can be easily polymerized on anode to give various morophology according to doped anion on electroactive sites. To improve the properties of brittleness, ageing and hydrophobisity, poly furan polymer(pfu) having a high initiation potential was anodically implanted in this porous ppy film matrix to get the Pt/ppy/pfu(x)type of polymer composite electrode. Cyclic voltammetry and electrochemical impedance methods were used to these electrode, where $PF_6^-,\; BF_4^-$, and $ClO_4^-$ ions were employed as dopants. The composition of the pfu(x) at the electrode was changed from 0 to 1.10, but the range was useful only at 0.1 to 0.2 as the redox electrode. The polymer composite electrode doped with $PF_6^-$ was better in charge transfer resistance by a factor of 40 times and in double layer capacitance by a factor of 20 times than others. The charge transfer in the polymer film of the electrode was influenced on frequency change and equivalent circuit of this electrode had Warburg impedance including mass transfer.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.251-259
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• 2005

In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

• 한국전기화학회:학술대회논문집
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• 1998.10a
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• pp.74-74
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• 1998

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2005-2010
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• 2009

Water droplet ejection characteristics of a point-to-plate airgap, with a wet porous point as a corona electrode, has been investigated. And the water droplet traces, charge, mass and number were measured experimentally. More particles are observed with wet porous point than metal point because the corona-discharging wet porous point can eject a number of water droplets. The water droplets ejected from the positive-corona-discharging wet porous point showed very fine traces as compared with those from the negative-corona-discharging wet porous point. Moreover, the water droplets ejected from the AC-corona-discharging wet porous point showed granular-like larger traces. It was shown that the weak corona discharge can eject smaller water droplets with larger ratio of mass-to-charge than the intense corona discharge.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.527-534
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• 2015

This study offers a novel method for improving the physical contact between the anode and fuel in a direct carbon fuel cell (DCFC): a direct generation of carbon in a porous Ni anode through the thermal decomposition of gaseous hydrocarbons. Three kinds of alkane hydrocarbons with different carbon numbers (CH4, C2H6, and C3H8) are tested. From electron microscope observations of the carbon particles generated from each hydrocarbon, we confirm that more carbon spheres (CS), carbon nanotubes (CNT), and carbon nanofibers (CNF) were identified with increasing carbon number. Raman scattering results revealed that the carbon samples became less crystalline and more flexible with increasing carbon number. DCFC performance was measured at $700^{\circ}C$ with the anode fueled by the same mass of each carbon sample. One-dimensional carbon fuels of CNT and CNF more actively produced and had power densities 148 and 210 times higher than that of the CS, respectively. This difference is partly attributed to the findings that the less-crystalline CNT and CNF have much lower charge transfer resistances than the CS.

• Analytical Science and Technology
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• v.7 no.3
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• pp.371-378
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• 1994

The detection range of this galvanic oxygen sensor for oxygen concentration was 0.0% to 20.0%. By using gold or silver as cathode, reproducible response time and sensitivity to change of oxygen concentration were observed. The anode was Pb-Sn-Ca alloy. Oxygen selective permeable membrane was hydrophobic and porous Teflon film. The effect of the membranes varying in thickness have been studied on the temperature($10{\sim}50^{\circ}C$) and relative humidity(R. H 0~99%). Lead acetate buffer solution as the electrolyte has shown a high output voltage and longer life.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.121-129
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• 2015

The platinum anode for the electrolytic reduction process is generally surrounded by a nonporous ceramic shroud with an open bottom to offer a path for $O_2$ gas produced on the anode surface and prevent the corrosion of the electrolytic reducer. However, the $O^{2-}$ ions generated from the cathode are transported only in a limited fashion through the open bottom of the anode shroud because the nonporous shroud hinders the transport of the $O^{2-}$ ions to the anode surface, which leads to a decrease in the current density and an increase in the operation time of the process. In the present study, we demonstrate the electrolytic reduction of 1 kg-uranium oxide ($UO_2$) using the porous shroud to investigate its long-term stability. The $UO_2$ with the size of 1~4mm and the density of $10.30{\sim}10.41g/cm^3$ was used for the cathode. The platinum and 5-layer STS mesh were used for the anode and its shroud, respectively. After the termination of the electrolytic reduction run in 1.5 wt.% $Li_2O-LiCl$ molten salt, it was revealed that the U metal was successfully converted from the $UO_2$ and the anode and its shroud were used without any significant damage.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.542-548
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• 1996

Electrodes modified with threonine, methionine and serine as ligands, which are incorporated by ion exchange into a polycationic film of electropolymerized $[Ru(v-bpy)_3]^{2+}$, have been employed in the determination of mercury in solution. The redox response of the surface-immobilized mercury/ligand complex was used as the analytical signal. When the polymeric film was electropolymerized, the supporting electrolytes were TBAP and $KPF_6$ to compare the morphology and anodic stripping of resulted polymer electrodes. At the case of the latter, the film had high porosity to give an easy incorporation of dopant anions into polymeric film matrix and a high sensitivity in determination of mercury ion. Especially, this polymer modified electrode exhibited possibility of multiple use in mercury determination over ten times. In all cases, calibration curves which were plotted by log of the surface coverage-normalized redox response vs. log[Hg] exhibited an excellent correlation (r=0.99) for mercury concentrations ranging from 1.0{\times}10^{-8}{\sim}1.0{\times}10^{-2}M$. At these curves relative standard deviation was 5∼8% and saturation response was not observed at high concentration region. Serine of the employed ligands had the best sensitivity in analytical application, which had greater stability constant in forming a complex with mercury than others as $pK_{Hg}=8.54$. The formation constants of threonine and methionine were respectively 7.04 and 7.80.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.436-436
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• 2014

본 연구에서는 전 세계적으로 활발히 연구되고 있는 나노바이오센서 분야 중 가장 주목을 받고 있는 LSPR 원리를 이용한 바이오센서를 제작하였다. 금속 나노입자의 국소 표면 플라즈몬 공명현상에 의한 주위환경에 민감하게 반응하는 특성은 고감도 광학형 바이오센서, 화학물질 검출 센서등에 응용된다. 특히 금 나노막대와 같은 1차 나노구조물은 나노막대의 주변 환경 변화에 따라 뚜렷한 플라즈몬 흡수 밴드 변화를 나타냄으로 센서로 적용 했을 때 고감도의 측정이 가능하다. 본 연구에서는 다공성인 알루미늄 양극산화 박막 주형틀을 이용하여 다양한 종횡비를 가지는 금 나노막대를 합성하고, 나노막대 어레이 형태의 박막을 제작하였다. 금 나노막대의 합성은 알루미늄 양극산화막을 사용한 주형제조 방법(template method)을 사용하는 전기화학 증착법을 사용하였다. 우선 부도체인 알루미늄 양극 산화막의 한쪽면을 열증착 장비를 사용하여 금을 증착하여 작업 전극(working electrode)을 형성하였다. 백금 선(platinum wire)을 보조 전극(counter electrode)으로 사용하고 Ag/AgCl 전극을 기준 전극(reference electrode)으로 사용하여 삼전극계(three-electrode system)를 형성하였으며, 금 도금 용액(orotemp 24 gold plating solution, TECHNIC INC.)을 사용하여, 800 mV 전압에서 금 나노 막대를 합성하였다. 금 나노막대의 길이는 테플론 챔버를 통과한 전하량 또는 전기 증착 시간에 비례하여 결정된다. 금 나노막대를 성장시킨 알루미늄 양극산화막을 실리콘 웨이퍼에 은 페이스트를 사용하여 고정시킨 후 수산화나트륨 (NaOH)용액을 사용하여 알루미늄 양극산화막을 녹여내어 수직방향으로 정렬되어 있는 나노 막대 어레이 박막을 제조 하였다. 또한 제작된 금 나노막대 어레이의 광학적 특성을 평가하였다. 본 연구에서와 같이 나노막대를 직경방향으로 측정할 경우, 직경방향의 transverse mode만 측정된다. 금 나노 막대가 알루미늄 양극산화막 안에 포함된 상태로 측정된 금 나노로드 어레이 박막의 광 스펙트럼 분포는 금 나노막대의 가시광영역에서의 흡수 스펙트럼을 측정하였을시 직경 및 길이에 따라 transverse mode의 ${\lambda}$ max (최대 흡광)의 위치가 변화됨을 나타낸다. 실험 결과를 바탕으로 나노막대의 종횡비가 증가함에 따라 흡수 스펙트럼의 transverse mode ${\lambda}$ max가 미약하게 단파장 영역으로 이동하는 것을 확인할 수 있다. 이러한 결과는 원기둥 형태의 금 나노막대의 흡수 스펙트럼에 대한 이론적인 예측과 부합한다. 바이오센서로의 적용 가능성을 확인하기 위하여 자기조립단분자막을 형성하여 항체를 고정하고 CRP에 대한 응답특성을 평가하였다. CRP 항원-항체의 면역반응에 대한 실험 결과 CRP 항원의 농도가 증가함에 따라 넓은 측정범위에서 선형적으로 흡광도가 증가하는 결과를 나타내었으며, CRP 10 fg/ml의 농도까지 검출할 수 있었다. 센서의 선택성을 확인하기 위하여 감지하고자하는 대상물질이 아닌 Tn T 항원을 감지막에 반응시켜 흡광도 변화를 분석하였다. 결과적으로 제작된 센서칩은 선택성을 가지고 측정하고자하는 물질에만 반응함을 확인하였다. 이러한 결과는 다양한 직경을 사용한 부가적인 LSPR현상의 연구에 활용될 수 있을 것이다.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.57-64
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• 2014

Carbon electrodes for capacitive deionization were fabricated through mixing two different carbon powders (activated carbon powder, carbon black) with different particle sizes to investigate physical or electrochemical properties and finally desalination performances of the electrodes with various compositions of two carbon powders in weight and were compared with the electrode consisting of activated carbon. As a result, the electrode structure became more packed as increasing the amount of carbon black and resulted in 10% increase in mesopore fraction. The specific capacitance obtained from cyclic voltammograms of various electrodes showed that the electrode containing carbon black only had 107.4 F/g, while the specific capacitance of the electrode having more amount of carbon black increased and was higher than the one having no carbon black. The results of desalination runs in a capacitive deionization cell exhibited that the electrode having the highest amount of carbon black (1 wt%) in this study had the highest desalting efficiency, and no significant pH variation was observed during the runs. It was analyzed using accumulated charge that the fraction of non-Faraday current increased as the amount of carbon black increased in the electrodes. It can be concluded that the addition of carbon black changed the electrode structure resulting in an increase in the fraction of mesopore and finally enhanced the desalting efficiency by decreasing Faraday current.