• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.483-489
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• 2007

Polyaniline (PANI)/Polyimide (PI) membranes were prepared and the effects of PANI contents and doping on the structural properties and gas separation properties were studied. The polyamic acid (PAA) solution was prepared by the polycondensation reaction of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4'-oxydianiline (ODA) in 1-methyl-2-pyrrolydinone (NMP) solvent. The PANI/PI blends were obtained by mixing PAA solution and PANI solution, and were doped with 1 M aqueous HCl solution for 24 h. The structural characterizations of the as-cast and doped membranes were examined by FT-IR, XRD, and TGA. The gas permeation experiments with $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ were carried out by variable pressure method at $30^{\circ}C$ and 5 atm. For all gases tested, the permeability coefficients of the blends decreased with increasing PANI content and the magnitude of permeability was in the order of $H_2$ > $CO_2$ > $O_2$ > $N_2$ > $CH_4$. The permeability for PANI/PI membranes decreased after the doping process while the permselectivity increased. For $H_2/CH_4$ separation, the doped PANI/PI (75/25) membrane has a permselectivity of 991.

• Polymer(Korea)
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• v.38 no.6
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• pp.687-693
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• 2014

Poly(ether-block-amide) 1657 (PEBAX 1657) blended membranes with molecular weight 400 poly(ethylene glycol) (PEG 400) were prepared and their permeability was tested for the gases $N_2$, $O_2$, $CH_4$, $CO_2$, and $SO_2$ by the time-lag method. The permeation characteristics were investigated in terms of diffusivity and solubility, which are dominant factors for gas transport. With the addition of PEG 400, the permeability of all the gases increased and also the ideal selectivity for several pair gases was enhanced. In particular, selectivity for $CO_2/N_2$ ranged from 53.2 (pristine PEBAX 1657 membrane) to 84.1 (50% PEG 400 added), for $SO_2/CO_2$ from 38.9 to 50.7, and for $CO_2/CH_4$ from 17.7 to 31.4. The increase of both permeability and selectivity is mainly because of the increase of solubility of the gases, especially $CO_2$ and $SO_2$. To obtain durability against water vapor, glutaraldehyde (GA) was added to the PEBAX 1657/PEG 400 blended membranes. As a result, permeability decreased owing to a reduction of the free volume and ether oxide units, which are the main factors in elevating the permeability for the blended membranes, and selectivity decrease however; we believe that the durability of the resulting membranes would be increased.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.196-201
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• 2001

The dependence of CoFe interfacial layer thickness and plasma oxidation condition on tunneling magnetoresistance (TMR) in Ta/NiFe/FeMn/NiFe/Al$_2$O$_3$/NiFe/Ta tunnel junctions was investigated. As the CoFe layer thickness increases, TMR ratio rapidly increases to 13.7 % and decreases with further increase of the CoFe layer thickness. The increase of TMR with the CoFe thickness up to 25 was thought to be due mails to the high spin-polarization of CoFe. The maximum MR of 15.3% was obtained in the Si(100)/Ta(50 )/NiFe(60 )/FeMn(250 )/NiFe(70 )/Al$_2$O$_3$/NiFe(150 )/Ta(50 ) magnetic tunnel junction with a 16 Al oxidized for 40 sec using a Ar/O$_2$ (1:4) mixture gas.

• Journal of Surface Science and Engineering
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• v.32 no.2
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• pp.165-171
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• 1999

The etching reaction of $UO_2$ in $CF_4/O_2$ gas plasma is examined as functions of $CF_4/O_2$ ratio, plasma power, and substrate temperature at up to $370^{\circ}C$ under the total pressure of 0.30 Torr. It is found that the highest etching rate is obtained at 20% $O_2$ mole fraction, regardless of r. f. power and substrate temperature. The existence of the optimum $CF_4/O_2$ ratio is confirmed by SEM, XPS and XRD analysis. The highest etching reaction rate at $370^{\circ}C$ under 150W exceeds 1000 monolayers/min., which is equivalent to 0.4$\mu\textrm{m}$/min. The mass spectrometry analysis results reveal that the major reaction product is uranium hexa-fluoride $UF_6$. Based on the experimental findings, dominant overall reaction of uranium dioxide in $CF_4/O_2$ plasma is determined : $8UO_2+12CF_4+3O_2=8UF_6+12CO_{2-x}$ where $CO_{2-x}$ represents the undetermined mix of $CO_2$ and CO.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.843-849
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• 2012

When we use NiO based particle as an oxygen carrier in a chemical looping combustion system, the fuel conversion and the $CO_2$ selectivity decreased with increasing reaction temperature within high temperature range (> $900^{\circ}C$) due to the increment of exhaust CO concentration from reduction reactor. To improve reduction reactivity at high temperature, the applicable metal oxide component was selected by calculation of the equilibrium CO concentration of metal oxide components. After that, feasibility of reduction reactivity improvement at high temperature was checked by using solid mixture of the selected metal oxide particle and NiO based oxygen carrier. The reactivity was measured and investigated using batch type fluidized bed. The solid mixture of $Co_3O_4/CoAl_2O_4$(10%) and OCN706-1100(90%) showed higher fuel conversion, higher $CO_2$ selectivity and lower CO concentration than OCN706-1100(100%) cases. Consequently, we could conclude that improvement of reduction reactivity at high temperature range by adding some $Co_3O_4$ based oxygen carrier was feasible.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.691-694
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• 2009

TBAB (Tetra-n-butyl ammonium bromide)는 상압에서 semi-clathrate를 형성하는 물질로서 최근 열역학적 촉진제 및 기체 저장 물질로서 주목받고 있다. 본 연구에서는 가스 하이드레이트 형성 시TBAB가 열역학적 촉진제로서 미치는 영향을 알아보기 위해 다양한 농도 (5, 10, 40, 60 wt%)의 TBAB를 $CH_4\;+\;H_2O$계, $CO_2\;+\;H_2O$계, $N_2\;+\;H_2O$계에 첨가하여 가스 하이드레이트 3상 평형 (H - LW - V)을 측정 하였다. 실험 결과 TBAB의 조성에 따른 촉진경향은 각 계가 유사하지만, 촉진 정도는 $N_2\;+\;H_2O$ 계가 앞의 두계에 비해 월등히 큰 것을 알 수 있었다. 또한, TBAB 농도가 40 wt% 일때 촉진효과가 가장 크게 나타났으며, 그 이상의 농도에서는 반대로 촉진효과가 감소하는 것을 알 수 있었다. 이는 혼합 하이드레이트 형성에 참여하지 못한 TBAB가 가스 하이드레이트 형성을 억제하기 때문으로 사료된다. 결과적으로 가스하이드레이트 공정에 TBAB를 열역학적 촉진제로서 적용할 경우 촉진효과가 가장 큰 40 wt% 범위의 농도로 사용하는 것이 가장 적절할 것으로 사료된다. 본 실험에서 얻어진 결과는 가스 하이드레이트 형성을 이용한 천연가스 수송/저장법을 위한 연구뿐만 아니라 기체 분리 공정 개발과 관련된 연구의 중요한 기초 자료가 될 것이다.

• Polymer(Korea)
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• v.28 no.5
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• pp.374-381
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• 2004

Gas permeability of low density polyethylene (LDPE) film containing zeolite powder for $CO_2,\;O_2$ and $N_2$ were investigated. Zeolite powders modified by cations or surfactant were compounded with LDPE to produce $20 wt\%$ masterbatch. After blending the masterbatch with LDPE, zeolite filled films were prepared by the blown film process. Finally, the composite films containing zeolite loadings of 0, 3,5, and $10 wt\%$ were produced. A gas permeability apparatus based on the variable volume principle was designed to analyze the characteristics of films. Experiments showed a general trend that gas permeabilities first decreased and then increased as the zeolite content was increased. Surfactant modified zeolite showed a better interfacial adhesion with the matrix, but the film did not show a discernible difference in gas permeability compared with the other modified films. The difference of temperature dependences in the gas permeabilities of composite films was slightly smaller than that of LDPE film.

• Membrane Journal
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• v.23 no.6
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• pp.432-438
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• 2013

Mixed-matrix membranes (MMMs) containing MIL-100(Fe), a MOF type, were fabricated in this study. MMMs up to 30 wt% MOF loading were prepared, and their gas permeabilities were tested. $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ gas permeabilities increased with the MOF loading, while $SF_6$, the largest kinetic diameter in this study, exhibited reduction of gas permeability with the loading. Ideal gas selectivity of $N_2/SF_6$ improved by 40% as compared with pure polyimide membrane, suggesting the proposed MMMs were suitable for $N_2/SF_6$ separation.

• Membrane Journal
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• v.23 no.2
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• pp.144-150
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• 2013

In order to increase the permeabilities of $N_2$, $O_2$, $CH_4$, $CO_2$, $SO_2$, Poly (ether block amides) (PEBAX) 3533 and its blended membranes with Poly (ethylene glycol) (PEG) of molecular weight 400 were prepared. The contents of PEG400 were 20%, 40%, and 50% and this membranes were characterized in terms of permeability for $N_2$, $O_2$, $CH_4$, $CO_2$, $SO_2$ gases and also diffusivity and solubility as well by using the time-lag gas separation apparatus. As expected, the permeabilities incerased as the contents of PEG400 increased. For the ideal selectivity, there is no big difference in values of between PEBAX 3533 and PEBAX/PEG400 membranes. The increase of permeabilities is due to the increases of solubilities of gases in question and this will be explained in more detail.

• Membrane Journal
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• v.17 no.3
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• pp.254-268
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• 2007

Sodium type faujasite(FAU) zeolite layers with diverse materials characteristics(Si/Al ratio, thickness, and structural discontinuity) were hydrothermally grown on a porous $\alpha-Al_2O_3$ tube, and then the $CO_2/N_2$ separation was evaluated at $30^{\circ}C$ for an equimolar mixture of $CO_2$ and $N_2$. Among hydrothermal conditions, $SiO_2$ content in hydrothermal solution seriously affected materials characteristics: with an increment in the $SiO_2$ content, Si/Al ratio, thickness, and structural discontinuity of grown FAU zeolite layer simultaneously increased. The present study reveals that structural discontinuity(intercrystalline voids due to an incomplete densification and cracks induced by GIS Na-P1 phase) is the most important variable affecting the $CO_2/N_2$ separation. Also, it was suggested that the $CO_2$ desorption in permeate side be the rate-determining(slowest) step in the overall $CO_2$ permeation.