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안정욱(JeongUk Ahn),안승균(SeongGyun Ahn),여인웅(InWoong Lyo),김형익(HyeongIk Kim),김웅(Woong Kim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
We have developed a well designed sputter DLC coating on valve lifter, which has reduced the mechanical friction by 40% and improved the fuel efficiency by 0.8%. This paper is focusing on mutual correlation between friction characteristic and the microstructure of DLC such as hydrogen concentration, sp3/sp2 ratio and I(D)/I(G).
알루미늄 밸브스프링 리테이너용 내마모 DLC 코팅기술 개발
안정욱(Jeong-Uk Ahn),안승균(Seong-Gyun Ahn),김형익(Hyung-Ik Kim),전영하(Young-Ha Jun) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The use of light-weight materials in automotive engine components has increased in order to achieve better fuel efficiency and engine performance. In this study, Al alloy(Al5056) valve spring retainer can reduce a weight by 63% in comparison to steel and improve the upper limit of engine speed by about 500rpm. The Al valve spring retainer was fabricated by cold forging and coated with hard anodizing, DLC(diamond like coating), cold spray and thermal spray for better wear resistance and durability. We conclude that among these materials the DLC coating improves the wear resistance of Al valve spring retainer and has a sufficient durability after endurance testing.
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.
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.