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전유택(Jeon, Yoo-Taek),정경우(Chung, Kyeong-Woo),나상묵(Na, Sang-Mook) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
Bipolar plate is the main part with MEA in automotive PEMFC. It must have a good electrical conductivity and excellent corrosion resistance, be cost effective. Therefore, stainless steels have been studied by many researchers because of its corrosion resistance and cost benefits. But their properties are not sufficient for the application to bipolar plate for automotive PEMFC. In this work, we have performed stamping using various commercial stainless steels to select candidate material for biploar plate and to derive design parameters for stamping simulation. The results showed that a small curvature at the corner of flow field is more favorable due to easier a plastic deformation. Stamping process was simulated by changing surface condition, and the size and angle of channel. The optimum shape and spring back phenomena were evaluated. Surface coating was applied to increase the corrosion resistance and electrical conductivity of stainless steel. The electrical interfacial resistance was 10 to 15m{Omega}cm² under clamping force of 150psi. But corrosion resistance of coating on the stainless steel was not good due to the unstableness of microstructure.
김근호(Kim, Kun-Ho),전유택(Jeon, Yoo-Taek) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.05
In order to achieve high performance and low cost for commercial applications, the development of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, must be optimized. Expensive platinum is currently used as an electrochemical catalyst due to its high activity. Although various platinum alloys and non-platinum catalysts are under development, their stabilities and catalytic activities, especially in terms of the oxygen reduction (ORR), render them currently unsuitable for practical use. Therefore, it is important to decrease platinum loading by optimizing the catalysts and electrode microstructure. In this study, we prepared several different MEAs (non-uniform Nafion^{(R)} ionomer loading electrode) which have dual catalyst layers to find the optimal Nafion^{(R)} ionomer distribution in the electrodes. We changed Nafion^{(R)} ionomer content in the layers to find the ideal composition of the binder and Pt/C in the electrode. For MEAs with various ionomer contents in the anodes and cathodes, the electrochemical activity (activation overpotential) and the mass transport properties (concentration overpotential) were analyzed and correlated with the single cell performance. The dual catalyst layers MEA showed higher cell performance than uniformly fabricated MEA, especially at the high current density region.
김근호(Kim, Kun-Ho),전유택(Jeon, Yoo-Taek) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11
For commercial applications, MEA development must be optimized in order to achieve high performance and low cost. There are many factors that affect the performance of MEA. Especially, the optimization of the method for preparing catalyst layer has great effect on the performance of MEA. Various methods have been used to prepare the catalyst layer of MEA. Among them, spraying method has a merit in that catalysis lay can be prepared with very flexible changes in catalyst layer as well as in the solvent composition of catalyst ink. In addition, in order to reduce the time required for manufacturing catalyst layer, an effort has been made to change the nozzle size and injection pressure of spray system. Further, the operation condition of spray system was changed in various ways in an effort to prepare optimum catalyst layer of MEA. Having optimized the operation condition of spraying system, comprehensive and diverse experiments were carried out concerning various factors that affect the performance of MEA. The present research report describes the results of more sub-categorized and more detailed experiments about the important factors (Nafion<sup>(R)</sup> ionomer, Relative humidity) which have been shown in previous experiments to exert greater effect on the performance of MEA.
이종찬(Lee, Jong-Chan),김기정(Kim, Ki-Jung),양유창(Yang, Yoo-Chang),전유택(Jeon, Yoo-Taek) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.06
The metallic bipolar plate in PEMFC is widely used for automotive driving because of its advantages, i) high strength, ii) high chemical stability, iii) low gas permeability and iv) applicability to mass production. Especially, the metallic bipolar plate which is manufactured with the sheet metal stamping process can be applied in automotive PEMFC with less volume and weight because of its thin thickness but the formability and springback problems arise in real manufacturing process. The assessment for formability and springback of metallic bipolar plate should be performed before making stamping die sets. In this work, the methodology for determining the allowable draft angle of flow passage is introduced by using finite element analysis. In analysis results, as the draft angle of flow passage increase, the major strain and thinning is increase with exponential function. The allowable draft angle without fracture is presented by fitting the results. Additionally, the staking results with manufactured metallic bipolar plates by stamping process is presented.
정경우(Chung, Kyeong-Woo),김세융(Kim, Se-Yung),양유창(Yang, Yoo-Chang),안승균(Ahn, Seung-Gyun),전유택(Jeon, Yoo-Taek),나상묵(Na, Sang-Mook) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11
Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below 19m{Omega}cm² under the compress force of 150N/cm². It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. 9{mu}A/cm² to ca. 0.5{mu}A/cm² in the mixed solution of 0.1N;N₂SO₄ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and 0.75V_{SCE} for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than 1{mu}A/cm² for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.
윤용식(Yun, Yong-Sik),정경우(Chung, Kyeong-Woo),양유창(Yang, Yoo-Chang),안승균(Ahn, Seung-Gyun),전유택(Jeon, Yoo-Taek),나상묵(Na, Sang-Mook) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11
As the stainless steel has good corrosion resistance, mechanical property and ease of manufacture, it has been studied as the candidate material of metallic bipolar plate for automotive PIMFC. But, metal is dissolved under fuel cell operating conditions Dissolved ions contaminate a membrane electrode assembly (MEA) and, decrease the fuel cell performance. In addition, metal oxide formation on the surface of stainless steel increases the contact resistance in the fuel cell. These problems have been acted as an obstacle in the application of stainless steel to bipolar plate. Therefore, many kinds of coating technologies have been examined in order to solve these problems. In this study, stainless steel was coated in order to achieve high conductivity and corrosion resistance by several methods. Contact resistance was measured by using a tensile tester and impedance analyzer Corrosion characteristics of coated stainless steel were examined by Tafel-extrapolation method from the polarization curves in a solution simulating the anodic and cathodic environment of PEMFC. Fuel cell performance was also evaluated by single cell test. We tested various coated metal bipolar plate and conventional and graphite were also tested as comparative samples. In the result, coated stainless steel bipolar plate exhibited better cell performance than graphite to bipolar plate.