• Carbon letters
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• v.1 no.3_4
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• pp.133-137
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• 2001

Mesoporous activated carbon fiber (ACF) was prepared from phenolic resin containing a small amount (0.1 wt %) of organic nickel complex through carbonization and steam activation. Microporous ACF as reference sample was also prepared from phenolic resin without agent. In both cases of the mesoporous ACFs and the microporous ACFs, the electric double layer capacitance of the nonaqueous electrolyte (0.5 M $TEABF_4$/PC or 1.0 M $LiClO_4$/PC) was not proportional to the BET specific surface area. This is owing to the low permeability of nonaqueous electrolyte or the low mobility of ion in narrow micropores. However, the mesoporous ACF showed higher double layer capacitance than the microporous (normal) ACF. This result suggests that the presence of many mesopores promotes the formation of effective double layer or the transfer of ion in the micropore.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.474-476
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• 2006

본 연구에서는 다양한 두께, loading 및 기공 구조를 갖는 MPL을 형성하여 DMFC용 확산층을 제조하였다. 본 실험에서 제조한 확산층의 경우, 두께가 증가하면서 기공이 micro-pore에서 meso-pore 영역으로 옮겨감을 확인할 수 있었으며, 또한 기공구조에 따라 공기 투과도 특성이 변화하는 것을 확인할 수 있었다 각각의 확산층은 서로 다른 운전 조건에서 우수한 성능(흑은 안정적인 성능)을 갖는 것으로 확인되었으며, 이는 용도에 따른 확산층의 적합한 구조 설계가 요구됨을 의미한다.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.181-188
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• 2001

The present research is an experimental study of subcooled flow boiling behavior using flat, microporousenhanced square heater surfaces in pure FC-72. Two $1-cm^{2}$ copper surfaces, one highly polished (plain) and one microporous coated, were flush-mounted into a 12.7 mm square, horizontal flow channel. Testing was performed for fluid velocities ranging from 0.5 to 4 m/s (Reynolds numbers from 18,700 to 174,500) and pure subcooling levels from 4 to 20 K. Results showed both surfaces' nucleate flow boiling curves collapsed to one line showing insensitivity to fluid velocity and subcooling. The log-log slope of the microporous surface nucleate boiling curves was lower than the plain surface due to the conductive thermal resistance of the microporous coating layer. Both, increased fluid velocity and subcooling, increase the CHF values for both surfaces, however, the already enhanced boiling characteristics of the microporous coating appear dominant and require higher fluid velocities to provide additional enhancement of CHF to the microporous surface.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.46-53
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• 2011

Water is continuously produced in polymer electrolyte membrane fuel cell (PEMFC), and is transported and exhausted through polymer electrolyte membrane (PEM), catalyst layer (CL), microporous layer (MPL), and gas diffusion layer (GDL). The low operation temperatures of PEMFC lead to the condensation of water, and the condensed water hinders the transport of reactants in porous layers (MPL and GDL). Thus, water flooding is currently one of hot issues that should be solved to achieve higher performance of PEMFC. This research aims to study liquid water transport in porous layers of PEMFC by using pore-network model, while the microscale pore structure and hydrophilic/hydrophobic surface properties of GDL and MPL were fully considered.

• Applied Microscopy
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• v.47 no.3
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• pp.101-104
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• 2017

In this investigation, synchrotron X-ray imaging was used to investigate the water distribution inside newly developed gas diffusion media in polymer electrolyte membrane fuel cells. In-situ radiography was used to reveal the relationship between the structure of the microporous layer (MPL) and the water flow in a newly developed MPL equipped with randomly arranged holes. A strong influence of these holes on the overall water transport was found. This contribution provides a brief overview to some of our recent activities on this research field.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.135-153
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• 1998

Nanofiltration (NF) is a recently introduced term in membrane separation. In 1988, Eriksson was one of the first authors using the word 'nanofiltration' explicitly. Some years before, FilmTech started to use this term for their NF50 membrane which was supposed to be a very loose reverse osmosis membrane or a very tight ultrafiltration membrane. Since then, this term has been introduced to indicate a specific boundary of membrane technology in between ultrafiltration and reverse osmosis. The application fields of the NF membranes are very broad as follows: Demeneralizing water, Cleaning up contaminated groundwater, Ultrapure water production, Treatment of effleunts containing heavy metals, Offshore oil platforms, Yeast production, Pulp and paper mills, Textile production, Electroless copper plating, Cheese whey production, Cyclodextrin production, Lactose production. The earliest NF membrane was made by Cadotte et al, using piperazine and trimesoyl chloride as monomers for the formation of polyamide active layer of the composite type membrane. They coated very thin interfacially potymerized polyamide on the surface of the microporous polysulfone supports. The NF membrane exhibited low rejections for monovalent anions (chloride) and high rejections for bivalent anions (sulphate). This membrane was called NS300. Some of the earliest NF membranes, like the NF40 membrane of FilmTech, the NTR7250 of Nitto-Denko and the UTC20 and UTC60 of Toray, are formed by a comparable synthesis route as the NS300 membrane. Commercially available NF membranes nowadays are as follows: ASP35 (Advanced Membrane Technology), MPF21; MPF32 (Kiryat Weizmann), UTC20; UTC60; UTC70; UTC90 (Toray), CTA-LP; TFCS (Fluid Systems), NF45; NF70 (FilmTec), BQ01; MX07; HG01; HG19; SX01; SX10 (Osmonics), 8040-LSY-PVDI (Hydranautics), NF CA30; NF PES 10 (Hoechst), WFN0505 (Stork Friesland). The typical ones among the commercially available NF membranes are polyamide composite membrane consisting of interfacially polymerized polyamide active layer and microporous support. While showing high water fluxes and high rejections of multivalent ions and small organic molecules, these membranes have relatively low chemical stability. These membranes have low chlorine tolerance and are unstable in acid or base solution. This chemical instability is appearing to be a big obstacle for their applications. To improve the chemical stability, we have tried, in this study, to prepare chemically stable NF membranes from PVA. The ionomers and interfacially polymerized polyamide were used for the modification of'the PVA membranes. For the detail study of the active layer, homogeneous NF membranes made only from active layer materials were prepared and for the high performance, composite type NF membranes were prepared by coating the active layer materials on microporous polysulfone supports.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1841-1844
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• 2014

• Journal of Periodontal and Implant Science
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• v.33 no.3
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• pp.499-518
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• 2003

The surface characteristics of titanium have been shown to have an important role in contact ossseointegration around the implant. Anodizing at high voltage produces microporous structure and increases thickness of surface titanium dioxide layer. The aim of present study was to analyse the response of rat calvarial osteoblast cell to commercially pure titanium and Ti-6A1-4V anodized in 0.06 mol/l ${\beta}$-glycerophosphate and 0.03 mol/l sodium acetate. In this study, rat calvarial osteoblasts were used to assay for cell viability and cell proliferation on the implant surface at 1,2,4,7 days. 1. Surface roughness was 1.256${\mu}m$ at 200V, and 1.745${\mu}m$ at 300V. 2. The thickness of titanium oxide layer was increased 1 ${\mu}m$ with the increase of 50V. 3. The proliferation rate of osteoblastic cells was increased with the increase of the surface roughness and the thickness of titanium oxide layer. 4. There was no difference in cell viability and cell proliferation between commercially pure titanium and Ti-6A1-4V anodized at the same condition. In conclusion, the titanium surface modified by anodizing was biocompatible, produced enhanced osteoblastic response. The reasons of enhanced osteoblast response might be due to reduced metal ion release by thickened and stabilized titanium dioxide layer and microporous rough structures.

• ETRI Journal
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• v.26 no.4
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• pp.285-291
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• 2004

We prepared a novel multi-functional dual-layer polymer electrolyte by impregnating the interconnected pores with an ethylene carbonate (EC)/dimethyl carbonate (DMC)/lithium hexafluorophosphate $(LiPF_6)$ solution. The first layer, based on a microporous polyethylene, is incompatible with a liquid electrolyte, and the second layer, based on poly (vinylidenefluoride-co-hexafluoropropylene), is submicroporous and compatible with an electrolyte solution. The maximum ionic conductivity is $7{\times}10^{-3}S/cm$ at ambient temperature. A unit cell using the optimum polymer electrolyte showed a reversible capacity of 198 mAh/g at the 500th cycle, which was about 87% of the initial value.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1177-1182
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• 2002

Highly surfaced and porous hydroxyapatite body was artificially formed on the surface of a shell through a reaction with phosphatic solutions. As a result of qualitative observation, hydroxyapatite seemed to be crystallized by solution-precipitation process accelerated by the nucleation surface of a shell. The process of formation of hydroxyapatite layer was as follows. 1. Dense nucleation and growth on the surface of solid phase 2. Formation of microporous layer by contact and entanglement between crystallines 3. diffusion of solution through the porous layer and thickness growth of layer towards inside