• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.737-746
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• 2008

Numerical study is conducted to grasp preferential diffusion effects on flame characteristics in $H_2/CO$ syn-gas diffusion flames diluted with $CO_2$. The models of Sun et al. and David et al., which have been well known to be best-fitted for $H_2/CO$ synthetic mixture flames. are evaluated for $H_2/CO$ synthetic mixture flames diluted with $CO_2$. Comparison of flame structures with mixture-averaged species diffusion and suppression of the diffusivities of $H_2$ and H was made. The behaviors of maximum flame temperatures with those species diffusion models are not explained by scalar dissipation rate but by the nature of chemical kinetics. Importantly-contributing reaction steps to heat release rate are also compared for the three species diffusion models in $H_2/CO/CO_2$ flames with and without $CO_2$ dilution.

• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.753-758
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• 2013

Molecular dynamics (MD) simulations have been used to study the diffusion behavior of small gas molecules ($CO_2$) in polyethylene terephthalate (PET)/polylactide (PLA) blends. The Flory-Huggins interaction parameters (${\chi}$) determined from the cohesive energy densities are smaller than the critical value of Flory-Huggins interaction parameters (${\chi}_{critical}$), and that indicates the good compatibility of PET/PLA blends. The diffusion coefficients of $CO_2$ are determined via MD simulations at 298 K. That the order of diffusion coefficients is correlated with the availably fractional free volume (FFV) of $CO_2$ in the PET/PLA blends means that the FFV plays a vital role in the diffusion behavior of $CO_2$ molecules in PET/PLA blends. The slopes of the log (MSD) as a function of log (t) are close to unity over the entire composition range of PET/PLA blends, which confirmes the feasibility of MD approach reaches the normal diffusion regime of $CO_2$ in PET/PLA blends.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.635-636
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• 2006

In this study, the diffusion behaviors of C and Co in liquid phase sintering of WC-Co system were investigated whether these two components diffused in the same direction in case of having opposite gradient each other with not being $\eta$ phase. The green compacts with controlled compositions in not being of $\eta$ phase and gradient composition which one is WC-5Co-1.2%C, the other is WC-XCo-0.2%C (where X = 5, 10, 15, 20, 25) were sintered at $1350^{\circ}C$ and $1400^{\circ}C$ and then the diffusion behaviors of C and Co were investigated by analyses of compositional change, also determined for microstructure and microhardness. Also, same testing was carried out on the specimens with dual layers sintered in upright and reverse positions to evaluate the effect of gravity on the diffusion in liquid Co. From the results of this study, we can find the fact that the direction of diffusion for C and Co in WC-Co system during liquid phase sintering was different and the effect of gravity for the liquid was insignificant. Also other physical properties were changed on the diffusion of elements.

• 한국가스학회지
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• 제8권3호
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• pp.43-51
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• 2004

GMS(generalized Maxwell Stefan) 모형을 이용하여 나노기공성 TPABr (Tetrapropylammoniumbromide) templating 실리카/알루미나 복합막에서 $CO_2$와 $N_2$의 투과 및 분리 특성을 해석하였다. 담체로 쓰이는 메조포러스 알루미나 지지체에서의 기체 투과는 누슨 확산 (Knudsen diffusion) 및 점성 확산 (viscous diffusion 혹은 Poiseuille flow)에 의존하였으며, 이러한 투과메커니즘은 DGM (dusty gas model)을 통하여 규명할 수 있었다. 본 연구에 사용한 복합막의 분리 특성을 결정 짖는 TPABr templating silica layer의 경우 강한 흡착 특성으로 인하여, 기공 확산보다는 표면 확산(surface diffusion)을 나타내었다. 따라서 GMS 모형을 통해 다성분계의 표면 확산 투과/분리 메커니즘을 성공적으로 해석할 수 있었다. 본 연구에서 사용된 복합무기막에서는 흡착량과 표면 확산 현상이 복합적으로 일어나기 때문에, 강흡착질인 $CO_2$와 비교적 약흡착질인 $N_2$ 혼합물 분리에 있어, $CO_2$의 pore-blocking 현상으로 인해 $CO_2$가 투과 농축되었다.

• 한국진공학회지
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• 제17권5호
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• pp.381-386
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• 2008

W(110) 표면에 성장한 Co 박막에서 원자 정역학을 주사터널링 현미경으로 연구했다. 원자섬의 개수 밀도를 측정하여 원자 확산 계수의 비를 알 수 있었다. W(110) 표면, Co가 1 원자층 성장된 표면, Co가 2 원자층 성장된 표면의 원자 확산 계수의 비는 상온에서 1:124:33000인 것으로 측정되었다. Co가 2 원자층 성장된 표면의 확산 계수가 Co 가 1 원자층 성장된 표면의 확산 계수보다 큰 것은 이종성장의 스트레인 효과로 인한 것으로 해석되었다.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.90-94
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• 1998

Self diffusion coefficients of $^{67}$Co and impurity diffusion coefficients of $^{51}$Mn and $^{65}$Zn in single crystalline CoO have been measured by applying different radioactive isotopes simultaneously. To compare the residual activity method and the tracer sectioning method we analyzed our tracer diffusion experiments by using both methods simultaneously. According to our experimental results, the diffusion coefficients obtained from both methods are identical within experimental error, demonstrating the relibility of our experimental procedures. The diffusion coefficients of all the isotopes obtained during these test experiments for the methodology are similar in magnitude and show similar dependences on oxygen partial pressure. These first observations indicate that impurity diffusion of Mn and Zn occur via a vacancy mechanism as known for self diffusion of cobalt.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.68-75
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• 2002

The dynamic behaviors of the single vortex and flame-vortex interaction in a $CH_4/Air$ diffusion flame with addition of $CO_2$ were investigated numerically. The numerical method was based on a predictor-corrector for low Mach number flow. A two-step global reaction mechanism was adopted as a combustion model. Through comparison of results by effect of $CO_2$ added either on the fuel or oxidizer side, it was found that the growth of single vortex and entrainment of surrounding fluid by $CO_2$addition on the fuel side are larger than those by $CO_2$ addition on oxidizer side. Also, when $CO_2$ is added on fuel side, flame-vortex interaction becomes more significant than on air side.

• 한국세라믹학회지
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• 제34권7호
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• pp.747-757
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• 1997

ZSM-5 zeolite composite membranes have been synthesized from a silica sol solution containing TPABr as an organic template by the dip-coating and the pressurized-coating hydrothermal treatment techniques. The CO2 separation efficiency of synthesized composite membranes was also investigated. The permeation mechanism of CO2 through ZSM-5 membranses was the surface diffusion, and that of N2, O2, and He gases was Knudsen diffusion or activated diffusion depending on the synthetic method of membranes and the measurement temperature. The CO2/N2 separation factor of the membrane prepared by the dip-coating hydrothermal treatment was 2.5 at about 12$0^{\circ}C$, while the ZSM-5 composite membrane synthesized by the pressurized-coating hydrothermal treatment technique showed the CO2/N2 separation factor of 9.0 at room temperature higher than that ever reported in the literature.

• 한국입자에어로졸학회지
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• 제11권2호
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• pp.29-36
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• 2015

The purpose of this research is to find out the collection property of nanoparticle in diffusion filter to know particle size dispersion of nanomaterial using inertial force and principle of Brownian diffusion motion. We used inertial filters which are two different type and diffusion filters made by various kinds of Wiremesh and the different pieces of filter to compare with particle size distribution using NaCl particles. Finally, We made a conclusion as follows : (1) the bigger available charging volume is and the larger specific surface area of inertial filter is, the better collection efficiency is. (2) The higher wire-mesh number of filter is, the more collection efficiency of small particle is increasing because the wire of the higher Wiremesh number filter is thinner and denser. (3) The more pieces of wire-mesh filter, the more collection efficiency is increasing because it makes the residence time longer.

• 한국세라믹학회지
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• 제24권5호
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• pp.484-490
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• 1987

Diffusion coupling experiment was done to study expansion of body and soild reaction in BaCO3-TiO2 system. Specimen of BaCO3 and TiO2 was formed with Pt-mark's method. Each specimen was fired at interval of 25℃ from 900℃ to 1000℃ for 2hrs. After that, specimen was fixed with resin and polished. Product layers of specimen were observed with SEM and EDS. The result were following; 1. Diffusion component is Ba2+, which diffuse toward TiO2. 2. Large crack between layer of BaCO3 and Ba2TiO4 was generated because of difference of thermal expansion coefficient. 3. Ba2TiO4 is formed to TiO2 body by the reaction of BaTiO3 and BaO and its structure is very porous. 4. BaTiO3 changes immediately to Ba2TiO4 by the reaction of BaO. But BaTiO3 which formed by the reaction of TiO2 and Ba2TiO4 exsists as layer because the diffusion distance of Ba2+ is far.