• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1117-1122
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• 2012

In order to study to apply the fuel cell, the study about the power system design and the load control is needed. However, to experiment the fuel cell need the auxiliary device and the complex control technology. For this reason the simulator is needed and such study is in progress actively. In this paper, the PEMFC (Polymer Electrolyte Membrane Fuel Cell) that is applied the vehicle, the small sized ship was simulated based on LabVIEW. The characteristic of fuel cell simulator was implemented based on a simulation data using the programmable power supply. The I-V characteristic according to various factors and the polarization curve of fuel cell were analysed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.311-320
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• 1998

The cryogenic fracture behaviors of austenitic stainless steel HN2 developed for nuclear fusion reactor were evaluated quantitatively by using the small punch(SP) test. The electrochemical polarization test was applied to study thermal aging degradation of HN2 steel. The X-ray diffraction(XRD) analysis was conducted to detect carbides and nitrides precipitated on the grain boundary of the heat treated HN2 steel. The mechanical properties of the HN2 steel significantly decreased with increasing time and temperature of heat treatment or with decreasing testing temperature. The integrated charge(Q) obtained from electrochemical polarization test showed a good correlation with the SP energy(ESP) obtained by means of SP tests. From the results observed in the x-ray diffraction and anodic polarization curve, it was known that the material the grain boundary. Combining SP test and electrochemical polarization test, it could be useful tools to non-destructively evaluate the cryogenic fracture behaviors and the aging degradation for cryogenic structural material.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.70-76
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• 2006

Micro-droplet cell with free droplet as a micro-electrochemical technique has been limited to apply to electrochemical systems with high wetting properties such as an acidic solution and low grade stainless steels(Type 316L). By loading negative pressure to a droplet, control of droplet size, and use of hydrophobic gasket, the cell is modified to be allowed to use for electrochemical systems with high wetting properties. For giving the reliability of new cell, studies on local corrosion were conducted for three different systems-an acidic chloride solution and high chromium ferritic stainless steel, the other acidic chloride solution and type 316, and a neutral chloride solution and type 316. stainless steel. Firstly, the modified micro-droplet cell allows the anodic polarization curves in an acidic chloride solution to show the fact that the local corrosion of high chromium stainless steel near the $\alpha/\sigma$ interface is due to the Cr depleted zone. Secondly, the local anodic polarization test of type 316 L in the other acidic chloride solution can be successfully conducted in the cell. Furthermore, the local polarization curves help elucidating the corrosion of type 316 with $\delta-ferrite$ phase. Finally, the polarization curves of type 316 L in a neutral chloride solution indicates that the factor affecting the pitting corrosion resistance was inclusions rather than $\delta-ferrite$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.139-139
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• 2017

최근 환경오염 문제로 인한 연비 규제 강화 속도가 빨라지고 있으며 이에 따른 연비 향상 기술이 크게 대두 되고 있다. 연비 향상 기술 중 경량화 방안소재로 알루미늄(Al), 마그네슘(Mg) 등의 비철금속을 주로 사용하고 있으며, 이중 알루미늄은 다른 경량화 금속소재보다 우수한 경쟁력을 가지고 있다. 하지만 경제적인 측면에서 철 대비 비용적인 어려움을 가지고 있고 용접성이 떨어지기 때문에, 자동차 부품의 일부만 알루미늄 소재를 선택하여 사용하고 있는 실정이며 알루미늄의 높은 이온화 경향으로 인해 기존 자동차 철강 소재와 접촉 시 쉽게 부식되는 단점을 가지고 있다. 이러한 문제점을 해결하기 위해서는 알루미늄의 금속원소를 첨가하는 연구가 지속적으로 개발 되고 있다. 알루미늄 합금에서 마그네슘의 첨가는 좋은 용접성과 내식성, 강도를 향상시킨다. 하지만 3%이상의 마그네슘 첨가는 입계에 ${\beta}(Al_xMg_y)$석출상이 석출되게 되며, 입계에 연속적으로 형성된 ${\beta}(Al_xMg_y)$석출상은 응력 부식 균열 (Stress corrsion cracking)과 입계 부식(Intergranular corrosion)을 야기하는 결과를 가져온다고 알려져 있다. 이 문제를 해결하기 위해 Al 5000계열 합금의 Zn의 첨가를 통해 ${\tau}(Al_xMg_yZn_z)$을 입계에 석출시켜서 입계에 ${\beta}(Al_xMg_y)$상의 석출을 방지함으로써 내식성을 향상시키거나 Al 5000계열 합금의 열처리를 통해 ${\beta}(Al_xMg_y)$석출상을 고용시킴으로써 응력부식균열의 발생을 억제하는 연구도 있다. 하지만 열처리 후 Polarization test를 이용한 내식성 연구는 잘 안 알려져 있다. 따라서 이번 연구에서는 Al5000계열의 주조한 합금을 DSC분석을 통하여 ${\beta}(Al_xMg_y)$석출상의 고용 온도가 약 $470^{\circ}C$라는 것을 확인한 후, 실온에서 $100^{\circ}C/hr$으로 가열하고 조건에 따라 $450^{\circ}C$에서 3시간, 6시간, 12시간, 24시간, 30시간 항온 유지시킨 후 공냉을 진행하였다. 열처리를 마친 시편은 에폭시를 이용하여 마운팅 하였으며, 시편표면을 2000#까지 연마 후 증류수로 세척한 다음 질소를 이용하여 건조 후 분극 시험을 진행하였다. 3.5wt% NaCl 용액에서 분극 곡선을 통해 부식거동을 확인한 결과 24시간까지 시간이 증가 할수록 내식성이 우수해지는 것을 확인하였으며, 추가적으로 조직사진, SEM & EDS 분석과 XRD, TEM 분석을 통해 내식성은 입계에 존재하는 Mg의 조성이 감소하게 되면 내식성이 향상되는 것을 관찰하였다.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.146-152
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• 2006

In micro electrochemical machining (ECM), electrodes should be prevented from unfavorable oxide and Passive layer formation on the machined surface or overall corrosion of the entire surface. Generally, metal electrodes corrode, passivate or dissolve in the electrochemical cell according to the electrode potential. Therefore, each electrode must maintain its stable potential. Tn this paper, the stable electrode potentials of tool and workpiece were determined using the potentiodynamic polarization test and verified experimentally considering machining stability and surface quality. Stable workpiece electrode potentials of two different passive materials of 304 stainless steel and nickel were determined in the 0.1 M sulfuric acid. Experimental results show good machined surface and fast machining rate using the determined electrode potentials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.05a
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• pp.108-108
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• 1998

일반적으로 탄소강은 수용액 중에 노출될 경우 전면부식에 의한 손상을 받는다. 그러나 부식방지를 위하여 부식억제제를 적용할 경우, 탄소강의 부식거동은 현저한 변화를 겪게된다. 이러한 부식거동의 변화는 첨가되는 부식억제제의 종류에 따라 분 류할 수가 있는데, 양극부식억제제, 음극부식억제제 그리고 이들의 혼합부식억제제로 분류할 수가 있다. 현장에 적용된 부식억제제 시스템 중에는 자동차용 부동액과 가스히터용 열전달 매체액이 있다. 이러한 부식억제제가 적용된 시스댐은 정확한 부식억제능의 평가에 의한 그 교체 시기의 결정이 매우 중요하다. 교체 시기가 빠를 경우, 유지비용이 과다하게 소요되는 문제가 있으며, 교체시기가 늦을 경우 설비의 부식을 초래하는 문제 가 있다. 따라서 부식억제제의 정확한 성능 평가법은 매우 중요하며, 이에 대한 다양 한 연구가 진행 중이다. 부식억제제가 함유된 용액의 부식억제성능을 평가하는 방법에는 대표적으로 무게 감량법을 이용하고 있다. 이 방법은 다종의 금속이 적용된 자동차용 부동액을 실제 사용조건과 유사한 실험 조건에서 단기간, 가혹조건에서의 무게 감량에 의해 부식억 제능을 평가하는 방법이다. 그러나 이러한 방법은 특히 국부부식이 진행될 경우 부 식억제능을 정량화 하는데 어려움이 있다. 한편 전기화학적 측정방법으로는 분극곡선법을 이용한 $E_P$(공식개시전위), $E_R$(재부동태 화전위)의 측정법이 있다. 또한 부식억제피막의 안정성을 측정하기 위한 방법으로 인 위적인 양극전류 인가에 의한 피막의 파괴후에 피막이 복원가능 여부 및 그 속도 측 정에 의해 부식억제제의 건전성을 확인할 수가 었다. 본 연구에서는 가스히터의 주구성 재료인 A210 Gr Al의 탄소강을 사용하여, 사용기간이 5년 이상되어 부식억제 기능을 거의 상실한 것으로 여겨지는 열전달 매체액 과 신규 부식억제제가 적용된 시스템 등 객관적으로 확인된 부식억제제 시스랩에 대 하여 다양한 평가 방법을 동원 비교분석하고자 하였다. 실험은 KSM 2142에 의한 무게감량법, 분극곡선 측정에 의한 $E_P$(공식개시전위), $E_R$(재부동태화전위) 측정, 시간에 따른 자연전위 변화 측정 빛 이때의 부식속도(선형분극법), 인위적인 피막 파괴 전,후 의 전위 변화 및 부식속도 측정법에 의한 국부부식 발달 저지능 등을 평가하여 각 실험결과를 비교분석하여 보았다.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.697-701
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• 2010

We investigate the cell performance and characteristics of a direct formic acid fuel cell (DFAFC) using palladium (Pd) as a catalyst for anode. Pd is deposited on the electrolyte using the "direct paint" method. From a continuous three time-test of the polarization curve of the DFAFC, it is found that the catalytic activity of Pd and the cell performance of DFAFC steadily degrade as the tests are proceeded. This behavior may be due to the deactivation of Pd by formate (COOH) and hydroxyl (OH) groups, which are electrochemically dissociated from formic acid solution. Estimations of the degradation, followed by reactivation in activity of Pd catalyst and DFAFC cell performance are implemented by linear voltage sweep tests going in both positive and negative directions. When the maximum voltage of 1.0 V versus DHE is applied to the cell while a linear voltage sweep test going in negative directions, the activity of Pd catalyst and the DFAFC cell performance recover by the rehabilitation in activity of the deactivated Pd.

• Journal of the Korean Chemical Society
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• v.17 no.5
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• pp.378-384
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• 1973

To investigate the mechanism of the reaction of electrolytic oxidation of iodide to iodate ions, polarization curves are determined in various kinds of solution using electrodeposited lead peroxide and platinum anodes. It was observed from the polarization curves that the limiting current is exists at concentration 1.5 M of potassium iodide, and these limiting current disappeared as potassium hydroxide was added up to concentration of 0.1 M. while in case of platinum anode, limiting current did not appear in dilute potassium iodide solution. These results are owing to the chemical reaction, $PbO_2+2I^{-}+2H^+{\to}PbO+I_2+H_{2}O$ ocurring at the surface of lead peroxide anode. Also, we studied to obtain the optimum conditions of electrolytic preparation of iodate from iodide solution using a cell without the diaphragm. The results are that; (a) addition of potassium dichromate at the anti-reducing agent is proper in concentration of 0.1 g/l, (b) electrolytic temperature is not so much effective in raising the current efficiency, (c) current efficiency is increased with current density, and (d) electrolysis is the most effective in weak alkaline solutions.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.473-480
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• 1996

Synthesis of n-perfluorooctanesulfonyl fluoride(n-PFOSF), which is valuable precursor perfluoro-chemicals, was studied by electrochemical fluorination(ECF). Of prime concern was to investigate the cyclic voltamograms of Ni electrode in anhydrous hydrogen fluoride(AHF) with and without the reactants and to measure fluorine evolution potential. In a batch cell, chronoampherometric electrolysis and various chemical analysis such as GC, GC/MS and IR were used to understand the amphere change of electrode and the reaction paths. Fluorine equilibrium potential was found to be about 2.8V(vs. $Cu/CuF_2$) from the cyclic voltammograms and decay curves of anode potential in AHF. In batch processes, the ECF proceeded in two distinguished steps. The first step proceeded electrochemically and the second one chemically. Under 7V(vs. $Cu/CuF_2$), amount of crude products was proportional to the applied anode potential. Above 7V(vs. $Cu/CuF_2$), it had a hundred percentage with weight ratio of reactants and productivity of PFOSF was almost constant.

• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.325-330
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• 1981

The electrochemical behavior of cadmium electrode for the nickel-cadmium battery system has been studied by cyclic voltammetry, controlled potential electrolysis and X-ray diffraction method. Cathodic polarization curve for cadmium hydroxide electrode prepared by electrochemical pretreatment of metallic cadmium showed two peaks. It has been found that cadmium hydroxide was reduced to cadmium metal at the first peak potential, whereas very activated metal of cadmium which was strongly oriented (002) rather than (101) was formed at the second peak potential. It was also found that the cadmium formed at the second peak potential reacted rapidly with oxygen. Therefore, it could be presumed that the cadmium recombination reaction with the oxygen was chemical, and could be represented as $2Cd + O_2 + 2H_2O\;{\longrightarrow}\;2Cd(OH)_2$.