Journal of the Korean Ceramic Society Vol. 45, No. 8, pp. 472~476, 2008. Multi-layered Coating Deposited on PEMFC (Proton Exchange Membrane Fuel Cell) Bipolar Plates Young-Hoon Yun, Hoon-Taek Chung, In-Su Cha, Jeong-Sik Choi, Dong-Mook Kim, and Jin-Ho Jung* Department of Hydrogen & Fuel Cell Technology, Dongshin University, Jeonnam 520-714, Korea *Department of Physics, Chonnam National University, Gwangju 500-757, Korea (Received July 3, 2008; Revised August 11, 2008; Accepted August 13, 2008) š w s v p d gq z Á zká Á Á½ Á y* w w * û w w (2008 7 3 ; 2008 8 11 ; 2008 8 13 ) ABSTRACT The surface region of commercial stainless steel 304 and 316 plates has been modified through deposition of the multi-layered coatings composed of titanium film (0.1 µm) and gold film (1-2 µm) by an electron beam evaporation method. XRD patterns of the stainless steel plates deposited with conductive metal films showed the peaks of the external gold film and the stainless steel substrate. Surface microstructural morphologies of the stainless steel bipolar plates modified with multi-layered coatings were observed by AFM and FE-SEM images. The stainless steel plates modified with 0.1 µm titanium film and 1 µm gold film showed microstructure of grains of under 100 nm diameter. The external surface of the stainless steel plates deposited with 0.1 µm titanium film and 2 µm gold film represented somewhat grain growth of Au grains in FE-SEM image. The electrical resistance and water contact angle of the stainless steel bipolar plates modified with multi-layered coatings were examined with the thickness of the gold film. Key words : Proton exchange membrane fuel cell (PEMFC), Bipolar plate, Gold film, Titanium film, Electrical resistance 1. š w (Proton Exchange Membrane Fuel Cell, PEMFC) y w œ l y š. š w w y w p xw k y w ã w š. 1-3) š w l y t ƒ w š k w w w s v p(bipolar plate). 4-6) š w bipolar plate š (graphite)» ƒœw w š, ƒœ š. 7) š w k bipolar plate 40% ƒ w, Corresponding author : Young-Hoon Yun E-mail : yunh2@dsu.ac.kr Tel : +82-61-330-3231 Fax : +82-61-330-3231 80% r. š w bipolar plate y w» w p û ƒ, w ƒœ,»,», û, û» n, w yw š w w y» w bipolar plate t p wetting. 7-9) š w bipolar plate w carbon polymer composites type, stainless steel metallic plate type š. Stainless steel» ƒœ, ƒ,»,» w, š w y w metallic plate w š w membrane bipolar plate t w y x w z w j., stainless steel t gq x j ƒ y š. 10-12) š w bipolar plate w ü» w j» w metal plate ü» w 472
noble metal coating x j š š. 10,11), š w bipolar plate» w j» w noble metal film w. š w bipolar plate stainless steel 304, 316 plate št x jš E-beam method w gold titanium metallic film w. Gold-titanium multilayered coating x stainless steel plate w XRD pattern w, bare stainless steel Gold-titanium multi-layered coating x stainless steel plate t» w d. Goldtitanium multi-layered coating x stainless steel plate x AFM SEM w, water contact angle. 2. x š w s v p d gq 473 š w bipolar plate stainless steel 304, 316 plate kw, titanium film gold film t w. Titanium film gold film E-beam method (Electron Beam Evaporator, World Science Co., Korea) y w š, 10 6 torr vacuum (in operation) ww. Titanium film 0.1 µm Ì, gold film 1µm 2µm Ì ƒƒ. 0.1 µm titanium film 15 min, 1 µm gold film, 2 µm gold film 30 min 60 min ƒƒ. SUS plate t 0.1 µm titanium film w z, 1 µm 2µm gold film w r w. Stainless steel t x titanium film gold film X-ray diffractometer (Xpert PRO, PAnalitical, The Netherlands) w y. Stainless steel multi-layered coating x plate» w I-V sourcemeter (Keithley, USA) w d w, ƒ : 500 µa ~ 5 A, current noise 5nA ü, d 1µV~40V d w.» w d plate t w two-point probeƒ w w d w. Surface morphology Scanning Probe Microscope (XE-200, PSIA corp. Korea) w Atomic Force Microscopy (AFM) mode mw, Field Emission Scanning Electron Microscope (FE-SEM, JSM 6700F, JEOL, Japan) w SEI mode t w. Stainless steel multi-film r w contact angle measuring system (Easydrop, KRUSS, Germany) w, water contact angle d w. 3. š 3.1. Multi-layered coating bipolar plate XRD pattern Fig. 1 stainless steel plate t external gold film titanium film multi-layered coating as-received stainless steel plates X-ray diffraction pattern ùküš. Multi-layered coating w t metallic bipolar plates stainless steel» w γ-fe phase pattern ùkü. Stainless steel plates t multi-layered coating X-ray diffraction pattern gold phase (external film, thickness: 1-2 µm) (111), (200), (220), (311) reflection 4 strong peaks (38.32 o, 43.81 o, 64.62 o, 77.58 o ) ùkü. Stainless steel t external gold film 0.1 µm thickness interlayer Fig. 1. XRD patterns of the stainless steel 304 plates deposited with Ti film and Au film. TA-110 (1 µm Au / 0.1 µm Ti), TA-120 (2 µm Au / 0.1 µm Ti) 45«8y(2008)
윤영훈 정훈택 차인수 최정식 김동묵 정진호 474 Fig. 2. AFM images of the stainless steel 304, 316 plates 서 증착된 titanium phase의 X-ray diffraction peak는 검출 되지 않았다. 3.2. Multi-layered coating이 증착된 bipolar plate의 surface morphology 관찰 Fig. 2는 external gold film (thickness:1-2 µm)와 titanium interlayer (thickness:0.1 µm)의 증착을 통해 표면이 개 질된 metallic bipolar plate들의 AFM surface morphology 를 나타내고 있다. Fig. 3은 external gold film 및 titanium film의 multi-layered coatings들로 증착된 stainless steel plates의 FE-SEM images를 나타내고 있다. Multilayered coating으로 개질된 stainless steel plate의 surface morphology에서는 대략 100 nm 정도의 직경을 가지는 입 자들이 관찰되었으며, external gold film의 thickness가 1 µm에서 2 µm으로 증가함에 따라 입자크기가 다소 증가 하는 경향을 나타냈다. 이것은 external gold film의 증착 과정 (deposition time:60 min) 동안 gold 입자의 grain growth이 발생한 것으로 판단되었다. 3.3. Multi-layered coating이 증착된 stainless steel bipolar plate의 resistance 분석 Fig. 4는 multi-layered coating이 증착된 stainless steel과 한국세라믹학회지 bare-sus 304, 316 plates의 resistance를 나타낸 것이다. 표면 개질된 stainless steel plate는 bare SUS plate들과 비교할 때 I-V plots과 resistance-current의 변화에 있어서, Fig. 3. FE-SEM images of the stainless steel 304, 316 plates (1-2 µm Au / 0.1 µm Ti film)
š w s v p d gq 475 Fig. 5. Contact angles of stainless steel 304, 316 plates TA-110 (1 µm Au / 0.1 µm Ti), TA-120 (2 µm Au / 0.1 µm Ti) Fig. 4. Resistance of the stainless steel 304, 316 plates TA-110 (1 µm Au / 0.1 µm Ti), TA-120 (2 µm Au / 0.1 µm Ti) x w ùkþ. External gold film thicknessƒ 1 µm 2µm ƒw,» w gold film Ì ƒ wt bipolar plate û electrical resistance ùkþ. t stainless steel 304, 316 plate w» w ùkþ, 2 µm gold film 0.1 µm titanium film gq SUS 304 r, ƒ û resistance ùkþ. 3.4. Multi-layered coating stainless steel bipolar plate water contact angle Fig. 5 bare stainless steel plate external gold film, titanium film multi-layered coating stainless steel plate w water contact angle d w. Bare-SUS 304, 316 plate 60, 70 ùkþ, Ti, Au metallic film stainless steel bipolar plate contact angle s³ 90 ùkü. Gold, titanium metallic film gq SUS 304 plate s³ 98.5 (gold film: 1 µm, titanium film: 0.1 µm) 99 (gold film : 2 µm, titanium film : 0.1 µm) water contact angle ùkþ. š w s v p w ƒ,, stainless steel t titanium interlayer external gold film mw t stainless steel plate water contact angle x w ƒ j ùkû. 4. External gold film (1-2 µm) titanium interlayer (0.1 µm) multi-layered coating stainless steel 304, 316 plate t electron beam evaporation process m w w. External gold film FE-SEM image m w surface morphology j» 100 nm ùkû. Gold film thickness j»ƒ ƒw w ùkþ. Multi-layered coatings metallic bipolar plates t w XRD pattern gold phase, (111), (200), (220), (311) reflection 4 strong peak. External gold film thickness 1µm l 2 µm¾ ƒ k t bipolar plate electrical resistanceƒ w w ùkþ. External gold film titanium film multi-layered coating stainless steel plate s³ 90-99 water contact angle ùkþ. Acknowledgment 2007 ( ) w w w (KRF-2007-313-D00322) REFERENCES 1. V. Mehta and J.S. Cooper, Review and Analysis of PEM Fuel Cell Design and Manufacturing, J. Power Sources, 114 32-53 (2003). 2. P. Coatamagna and S. Srinivasan, Quantum Jumps in the PEMFC Science and Technology from the 1960s th the Year 45«8y(2008)
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