• Title/Summary/Keyword: Diffusion layer

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Effect of Diffusion Layer for Cell Performance in DMFC (직접메탄올 연료전지에서 전지 성능에 대한 확산층의 영향)

  • Kwon Bu-Kil;Park Kyung-Won;Choi Jong-Ho;Sung Yung-Eun
    • 한국전기화학회:학술대회논문집
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    • 2001.06a
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    • pp.179-184
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    • 2001
  • The diffusion layer within MEA(membrane electrode assembly) has been evaluated important factor for improvement of cell performance in DMFC. The diffusion layer in MEA structure leads to the reduction of catalyst loss in active catalysts layer as well as prevention of water-flooding in cathode. Cell performance is directly affected by interior properties of diffusion layer materials. Acetylene Black and $RuO_2$ with large pore size and low porosity compared to Vulcan XC-72R gave better performance caused by vigorous methanol diffusion and water removal. And $RuO_2$ as diffusion layer materials showed different behavior in anode and cathode compartment, that is, diffusion layers in anode and cathode side make methanol diffusion and water removal facilitate, respectively.

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A study on ZrN layer as a diffusion barrier between Cu and Si (Cu와 Si 사이에서 확산방지막으로 사용하기 위한 ZrN 층의 연구)

  • 김창조;김좌연;윤의중;이재갑
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.11a
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    • pp.21-24
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    • 1998
  • The properties of ZrN layer deposited by Sputtering system have been investigated in the application of diffusion barrier layer to copper. ZrN layer exhibited a excellent barrier property up to $700^{\circ}$ and higher resistivity. If an excess $O_2$is protected during the process of ZrN deposition, ZrN layer will be possible to use a diffusion barrier layer to copper.

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Behavior of Diffusion Layer Formation for TiNi/6061Al Smart Composites by Vacuum hot Press (진공 Hot Press법에 의한 TiNi/6061Al 지적 복합재료의 확산층 형성거동)

  • Park, Kwang-Hoon;Park, Sung-Ki;Shin, Soon-Gi;Lee, Jun-Hee
    • Korean Journal of Materials Research
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    • v.12 no.12
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    • pp.955-961
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    • 2002
  • 2.7vol%TiNi/6061 Al composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum hot press. It was investigated by OM, SEM, EPMA and XRD analysis for the behavior of diffusion layer formation on various heat treatment condition. Thickness of diffusion layer was increased proportionally according to heat treatment time. The layer was formed by the mutual diffusion of TiNi and Al. The diffusion rate from TiNi fiber to Al matrix was faster than that of reverse diffusion path. The more diffused layer was formed in Al matrix. The diffusion at interface layer was consisted of $A1_3$Ti, $Al_3$Ni analyzed by EPMA, XRD results.

Reaction diffusion and formation of$Ni_3Al$ phase at the Ni-NiAl diffusion couple (Ni-NiAl 확산대에서 $Ni_3Al$ 상의 형성과 반응확산)

  • 정승부
    • Journal of Welding and Joining
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    • v.15 no.3
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    • pp.128-135
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    • 1997
  • Reaction diffusion and formation of $Ni_3Al$phase with $L1_2$ structure have been studied in temperature range of 1432K to 1573K using the diffusion couple of (Ni-40, 5at%Al)/(Ni-14, 1at%Al) and (Ni-49, 2at%Al)/ (Nickel). The layer growth of Ni$_{3}$Al pyhase in the annealed diffusion couple was measured by optical microscope and electron probe microanalyzer (EPMA). The layer growth of $Ni_3Al$phase in diffusion zone obeyed the parabolic law without any indication of grain boundary effects. The layer growth of $Ni_3Al$phase in temperature range of 1423K to 1573K was mainly controlled by the volume diffusion mechanism. The rate of layer growth of $Ni_3Al$phase was found to be colsely related to the composition of intermetallic compound NiAl phase. The activation energy for layer growth of $Ni_3Al$phase was calculated to be 127kJ/mol.

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THE EFFECT OF SI-RICH LAYER COATING ON U-MO VS. AL INTERDIFFUSION

  • Ryu, Ho-Jin;Park, Jae-Soon;Park, Jong-Man;Kim, Chang-Kyu
    • Nuclear Engineering and Technology
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    • v.43 no.2
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    • pp.159-166
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    • 2011
  • Si-rich-layer-coated U-7 wt%Mo plates were prepared in order to evaluate the diffusion barrier performance of the Si-rich layer in U-Mo vs. Al interdiffusion. Pure Si powder was used for coating the U-Mo plates by annealing at $900^{\circ}C$ for 1 h under vacuum of approximately 1 Pa. Si-rich layers containing more than 60 at% of Si were formed on U-7 wt%Mo plates. Diffusion couple tests were conducted in a muffle furnace at $560-600^{\circ}C$ under vacuum using Si-rich-layer-coated U-Mo plates and pure Al plates. Diffusion couple tests using uncoated U-Mo plates and Al-(0, 2 or 5 wt%)Si plates were also conducted for comparison. Si-rich-layer coatings were more effective in suppressing the interaction during diffusion couple tests between coated U-Mo plate and Al, when compared with U-Mo vs. Al-Si diffusion couples, since only small amounts of Al in the coating could be found after the diffusion couple tests. Si-rich-layer-coated U-7wt%Mo particles were also prepared using the same technique for U-7 wt%Mo plates to observe the microsturctures of the coated particles.

The Effect of Diffusion Barrier and thin Film Deposition Temperature on Change of Carbon Nanotubes Length (탄소나노튜브 길이 변화에 대한 확산방지층과 박막 증착 온도의 영향)

  • Hong, Soon-kyu;Lee, Hyung Woo
    • Journal of Powder Materials
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    • v.24 no.3
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    • pp.248-253
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    • 2017
  • In this study, we investigate the effect of the diffusion barrier and substrate temperature on the length of carbon nanotubes. For synthesizing vertically aligned carbon nanotubes, thermal chemical vapor deposition is used and a substrate with a catalytic layer and a buffer layer is prepared using an e-beam evaporator. The length of the carbon nanotubes synthesized on the catalytic layer/diffusion barrier on the silicon substrate is longer than that without a diffusion barrier because the diffusion barrier prevents generation of silicon carbide from the diffusion of carbon atoms into the silicon substrate. The deposition temperature of the catalyst and alumina are varied from room temperature to $150^{\circ}C$, $200^{\circ}C$, and $250^{\circ}C$. On increasing the substrate temperature on depositing the buffer layer on the silicon substrate, shorter carbon nanotubes are obtained owing to the increased bonding force between the buffer layer and silicon substrate. The reason why different lengths of carbon nanotubes are obtained is that the higher bonding force between the buffer layer and the substrate layer prevents uniformity of catalytic islands for synthesizing carbon nanotubes.

Limit-current type zirconia oxygen sensor with porous diffusion layer (다공성 확산층을 이용한 한계전류형 지르코니아 산소센서)

  • Oh, Young-Jei;Lee, Chil-Hyoung
    • Journal of Sensor Science and Technology
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    • v.17 no.5
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    • pp.329-337
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    • 2008
  • Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

Change in Microstructure and Coating Layer of Al-Si Coated Steel after Conductive Heating (Al-Si 도금강의 통전 가열에 따른 미세조직과 도금층 변화)

  • Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.34 no.3
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    • pp.107-115
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    • 2021
  • Al-Si coated boron steel has been widely used as commercial hot stamping steel. When the steel is heated at 900~930℃ for 5 min in an electric furnace, thickness of the coating layer increases as a consequence of formation of intermetallic compounds and diffusion layer. The diffusion layer plays an important roll in blunting the propagation of crack from coating layer to base steel. Change in microstructure and coating layer of Al-Si coated boron steel after conductive heating with higher heating rate than electric furnace has been investigated in this study. Conductive-heated steel showed the martensitic structure with vickers hardness of 505~567. Both intermetallic compounds in coating layer and diffusion layer were not observed in conductive-heated steel due to rapid heating. It has been found that the conductive-heating consisting of rapid heating to 550℃ which is lower than melting point of Al-Si coating layer, slower heating to 900℃, and then 1 min holding at 900℃ is effective in forming intermetallic compound in coating layer and diffusion layer.

The Effect of Liquid Water in Fuel Cell Cathode Gas Diffusion Layer on Fuel Cell Performance (가스 확산층(GDL)내부의 물이 연료전지 성능에 미치는 영향)

  • Park, Sang-Kyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.4
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    • pp.374-380
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    • 2015
  • In this paper, a dynamic model describing the 2 phase effect on the gas diffusion layer depending on load change of a fuel cell stack was developed to examine the effects of liquid water in fuel cell cathode gas diffusion layer on the fuel cell performance. For the developed model, 2 phase effect on the performance of a fuel cell stack depending on the load changes, concentration distribution of water vapor and oxygen inside a gas diffusion layer, the effect of the thickness and porosity of the gas diffusion layer on the fuel cell stack voltage were examined. As a result, a fuel cell stack voltage for the 2 phase model within the scope of the research become lower than that for the 1 phase model regardless of the load. Although oxygen molar concentration for the gas diffusion layer adjacent to the catalyst layer was the lowest, water vapor concentration is the highest. In addition, as thickness and porosity of the gas diffusion layer increased and decreased, respectively, the fuel cell stack voltage decreased.

Effect of Heat Treatment of the Diffusion Barrier for Bus Electrode of Plasma Display by Electroless Ni-B Deposition (무전해 Ni-B 도금을 이용한 플라즈마 디스플레이 버스 전극용 확산방지막의 열처리 영향)

  • Choi Jae Woong;Hwang Gil Ho;Hong Seok Jun;Kang Sung Goon
    • Korean Journal of Materials Research
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    • v.14 no.8
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    • pp.552-557
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    • 2004
  • Thin Ni-B films, 1 ${\mu}m$ thick, were electrolessly deposited on Cu bus electrode fabricated by electro deposition. The purpose of these films is to encapsulate Cu electrodes for preventing Cu oxidation and to serve as a diffusion barrier against copper contamination of dielectric layer in AC-plasma display panel. The layers were heat treated at $580^{\circ}C$(baking temperature of dielectric layer) with and without pre-annealing at $300^{\circ}C$($Ni_{3}B$ formation temperature) for 30 minutes. In the layer with pre-annealing, amount of Cu diffusion was lower about 5 times than that in the layer without pre-annealing. The difference of Cu concentration could be attributed to Cu diffusion before $Ni_{3}B$ formation at grain boundaries. However, the diffusion behavior of the layer with pre-annealing was similar to that of the layer without pre-annealing after $Ni_{3}B$ formation. With increasing annealing time, Cu concentration of both layers increased due to grain growth.