• Korean Chemical Engineering Research
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• 제51권4호
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• pp.432-437
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• 2013

고분자 전해질 연료전지 구동 시 양극 활성 물질에 대한 CO 피독을 방지하기 위해 Cu를 촉매 활성 종으로 사용하고 반응물의 확산이 용이한 몇 가지 메조 세공 물질을 지지체로 이용하여 CO 선택적 산화 반응(PROX반응)을 실시하였다. 그 결과 거대 세공을 가진 SBA-15를 지지체로 사용했을 때 우수한 CO 산화 활성을 보였으며 특히 Cu 담지 량에 비례하여 활성은 증가하였다. 또한 Cu의 분산도를 높이고자 첨가한 Ti 성분은 저온에서 CO 산화 성능을 높이는데 기여하였다. 특히 Ti 성분을 20 wt-% 첨가한 Cu/Ti20-SBA-15 촉매에서 Cu의 분산도가 가장 우수하였으며 CO 산화활성 역시 개선됨을 확인하였다.

• 한국연소학회지
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• 제6권2호
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• pp.1-7
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• 2001

In order to elucidate the turbulent burning velocity of the two-component fuel mixtures, the lean and rich two-component fuel mixtures, where methane, propane and hydrogen were used as fuels, were prepared keeping the laminar burning velocity nearly the same value. Clear difference in the measured turbulent burning velocity at the same turbulence intensity can be seen among the two-component fuel mixtures with different addition rate of fuel, even under nearly the same laminar burning velocity. The burning velocities of lean mixtures change almost monotonously as changing addition rate, those of rich mixtures, however, do not show such a monotony. These phenomena can be explained qualitatively from the local burning velocities, estimated by considering the preferential diffusion effect for each fuel component. In addition, a prediction expression of turbulent burning velocity proposed for the one-component fuel mixtures can be applied to the two-component fuel mixtures by using the estimated local burning velocity of each fuel mixture.

• 한국수소및신에너지학회논문집
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• 제15권1호
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• pp.12-22
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• 2004

In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP (normal temperature and pressure) condition in a constant-pressure combustion chamber. With propane being the substituent, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using a recent kinetic mechanism. Results show substantial reduction of laminar burning velocities with propane substitution, and support the potential of propane as a suppressant of both diffusional-thermal and hydrodynamic cellular instabilities in hydrogen-air flames.

• E2M - 전기 전자와 첨단 소재
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• 제10권10호
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• pp.1034-1040
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• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. Grain boundaries acted as potential barriers as well as recombination centers for the photo-generated carriers. To reduce these effects of the grain boundaries we investigated various influencing factors such as emitter thickness thermal treatment preferential chemical etching of grain boundaries grid design contact metal and top metallization along boundaries. Pretreatment in $N_2$atmosphere and gettering by POCl$_3$and Al were performed to obtain multicrystalline silicon of the reduced defect density. Structural electrical and optical properties of slar cells were characterized before and after each fabrication process. Improved conversion efficiencies of solar cell were obtained by a combination of pretreatment above 90$0^{\circ}C$ emitter layer of 0.43${\mu}{\textrm}{m}$ Al diffusion in to grain boundaries on rear side fine grid finger top Yb metal and buried contact metallization along grain boundaries.

• 한국표면공학회지
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• 제32권2호
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• pp.157-164
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• 1999

In this study the effect of nickel addition on the coating weight of mini-mill steels containing silicon has been studied. It is shown that the pure zinc accelerated growth of the alloy layers occurred by a rapid growth of the zeta phase at 0.06%Si. The addition of 0.06%Ni to a pure zinc bath was found to be very effective in reducing the coating weight and promoting preferential development of the delta phase. The coating obtained by immersion in the Zn-Ni bath shows the presence of a nickel-rich region between the zeta phase and the eta phase. It is suggested that nickel prevents the rapid growth of the zeta phase due to the formation of the Zn-Ni-Fe ternary compound, which may act as a barrier to inward diffusion of zinc or iron at the zeta-eta boundary.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• 대한기계학회논문집B
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• 제36권6호
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• pp.639-646
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• 2012

가열된 동축류 공기에서 일산화탄소/수소의 층류 제트에 대한 자발화된 부상화염의 특성을 조사하였다. 그 결과로 자발화가 발생하지 않는 영역에서는 제트속도의 증가에 따라 노즐부착화염에서 안정화된 층류 부상화염을 거치지 않고 바로 화염날림이 발생하였다. 자발화 영역에서, 질소 희석된 일산화탄소의 자발화된 부상화염은 산화제 내의 함유된 수분에 따른 점화지연시간의 변동으로 그 부상높이가 크게 영향을 받았다. 그리고 수소에 의한 저온 자발화 영역에서 자발화된 부상화염은 제트속도의 증가에 따라 부상높이가 감소하다가 증가하는 독특한 현상이 발생하였다. 점화지연시간에 의한 자발화된 층류 부상화염의 안정화 메커니즘을 기반으로, 그 부상높이의 거동은 점화 과정에서 발생하는 열손실의 영향뿐만 아니라 연료제트의 운동량과 질량의 선호 확산에 의하여 영향을 받을 수 있다는 것을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.286-286
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• 2010

The lack of homogeneously sized single-walled carbon nanotubes (SWNTs) hinders their many applications because properties of SWNTs, in particular electrical conduction, are highly dependent on the diameter and chirality. Therefore, the preferential growth of SWNTs with predetermined diameters is an ultimate objective for applications of SWNTs-based nanoelectronics. It has been previously emphasized that a catalyst size is the one crucial factor to determine the CNTs diameter in chemical vapor deposition (CVD) process, giving rise to several attempts to obtain size-controllable catalyst by diverse methods, such as solid supported catalyst, metal-containing molecular nanoclusters, and nanostructured catalytic layer. In this work, diameter-controlled CNTs were synthesized using a nanostructured catalytic layer consisting of Fe/Al2O3/Si substrate. The CNTs diameter was controlled by structural modification of Al2O3 supporting layer, because Al2O3 supporting layer can affect agglomeration phenomenon induced by heat-driven surface diffusion of Fe catalytic nanoparticles at growth temperature.

• Coupled systems mechanics
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• 제8권2호
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• pp.129-146
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• 2019

The main goal of this work is to develop a numerical simulator to study an isothermal single-phase two-component flow in a naturally fractured oil reservoir, taking into account advection and diffusion effects. We use the Peng-Robinson equation of state with a volume translation to evaluate the properties of the components, and the discretization of the governing partial differential equations is carried out using the Finite Difference Method, along with implicit and first-order upwind schemes. This process leads to a coupled non-linear algebraic system for the unknowns pressure and molar fractions. After a linearization and the use of an operator splitting, the Conjugate Gradient and Bi-conjugated Gradient Stabilized methods are then used to solve two algebraic subsystems, one for the pressure and another for the molar fraction. We studied the effects of fractures in both the flow field and mass transport, as well as in computing time, and the results show that the fractures affect, as expected, the flow creating a thin preferential path for the mass transport.

• 콘크리트학회논문집
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• 제19권6호
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• pp.707-715
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• 2007

다공질성 특성을 갖는 콘크리트는 충분한 다짐과 양생 조건에서 장수명을 갖으며, 유해 물질의 주요 경로는 공극이다. 그러나 균열이 발생한 콘크리트의 경우, 균열은 염소이온과 같은 유해 물질의 우선적인 침투 경로가 된다. 균열이 염소에 미치는 영향은 균열폭과 균열 깊이의 크기에 의존한다. 본 연구는 미세균열이 콘크리트의 염소이온 침투에 미치는 영향을 다룬 실험적 연구로서, 연구 목적은 균열폭과 균열 깊이 등의 균열 크기 효과가 염소이온에 미치는 영향을 고찰하는 것이다. 균열을 통한 염소이온의 침투를 시각화 하기 위하여, 급속 염소이온 침투 실험인 RCM (rapid chloride migration) 실험을 수행하였다. 균열폭과 균열 깊이는 전자 현미경으로 관찰하였고, 평균적인 균열폭을 산정하기 위하여 균열 개구 변위가 측정되었다. 다양한 균열 크기에 따른 염소이온의 침투 깊이 및 염소이온 확산계수의 변화율로부터 염소이온이 침투되지 않는 균열 깊이 및 이에 대응한 균열폭이 도출되었다.