• 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.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.631-636
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• 1997

This study was conducted to increase the adorption capacity of microporous carbon which is widely used as an adsorbent. After increasing the adsorption capacity of microporous carbon by heat-treatment, chromium($Cr^{+6}$) solution, which is the one of hazardous heavy metals, was selectively adsorbed on microporous carbon. Optimum temperature range for the heat-treatment of microporous carbon was $340{\sim}350^{\circ}C$, and the average specific surface area was measured as $1380m^2/g$ by BET (Brunauer-Emmett-Teller) method. The weight loss was about 10 percents during the heating to optimum temperature. However, It became a qualitative adsorbent due to a larger specific surface area. Removal of chromium($Cr^{+6}$) in solution by heat-treated microporous carbon was successfully carried out.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.105-110
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• 2018

The flow boiling heat transfer of water was experimentally investigated on plain and sintered microporous surfaces in a mini-channel. The effects of microporous coating on flow boiling heat transfer of subcooled water were investigated in a 300 mm long mini-channel with a cross section of $20{\times}10mm^2$. The test section has sufficiently long entrance length of 300 mm which provides a fully-developed flow before the channel inlet. The bottom side of the channel was heated by a copper block assembled with a high-density cartridge heater and other sides of the channel were insulated. The microporous surface was fabricated by sintering copper particles with the average particle size of $50{\mu}m$ on the top side of the copper block. Heat transfer measurement was conducted at the mass flux of $208kg/m^2s$ and the heat flux up to $500kW/m^2$. Microporous coated surface showed an earlier boiling incipience compared with plain surface regardless of the mass flux. Microporous coating were significantly attributed to local wall temperature and local heat transfer coefficient for flow boiling.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.94.2-94.2
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• 2011

In this work, multi-functional groups, i.e., nitrogen and oxygen, contained microporous carbons (MF-MCs) were prepared by the one step carbonization of the poly(vinylidene chloride-co-acrylonitrile-co-methyl methacryalte) (PVDC-AN-MMA) without activation. The electrochemical performance of MF-MCs was investigated as a function of carbonization temperature. It was found that MF-MCs had a high specific surface area over $800m^2/g$ without additional activation, resulting from the micropore's formation by the release of chlorine groups. In addition, although functional groups decreased, specific surface area was increased with increasing carbonization temperature, leading to the enhanced electrochemical performance. The pore size of the carbon distributed mainly in small micropore of 1.5 to 2 nm, which was idal for aqueous electrolyte. Indeed, the unique microstructure features, i.e. high specific surface area and optimized pore size provided high energy storage capability of MF-MCs. These results indicated that the microporous features of MF-MCs lead to feasible electron transfer during charge/discharge duration and the presence of nitrogen and oxygen groups on the MF-MCs electrode led to a pseudocapacitive reaction.

• Composites Research
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• v.31 no.5
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• pp.267-275
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• 2018

A facile method for the preparation of nitrogen-doped microporous carbon via the pyrolysis of poly(vinylidene fluoride) (PVDF) using polypyrrole (PPy) as a selective nitrogen source was developed. A PVDF/PPy-800 sample (carbonized at $800^{\circ}C$) with a 1:0.5 ratio of PVDF and PPy exhibited the highest micropore volume. The activated microporous carbon materials obtained from PVDF/PPy-800 prepared at $800^{\circ}C$ with KOH possessed a large specific surface area and narrow pore-size distribution. They were characterized using $N_2$ adsorption at 77 K and argon (Ar) adsorption at 87 K, which allowed for the characterization of the narrow microporosity of the prepared materials due to the absence of interactions between Ar and the sample surface. In addition, the activated microporous carbon material with a KOH/carbon ratio of 2:1 was found to exhibit the largest specific surface area ($1296m^2g^{-1}$ in $N_2$ at 77 K) and microporosity, and a high specific capacitance ($122.8F\;g^{-1}$).

• Membrane Journal
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• v.7 no.3
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• pp.123-130
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• 1997

The characteristics of microporous separator for lithium ion secondary battery was introduced. Microporous separator is a key component of a lithium ion secondary battery because its basic properties were related with the performance and safety of the battery. Up to now, stretched microporous polyolefins such as polyethylene(PE) separator were mainly applied. It is still required to enhance wettability and shut-down property. For this purpose, the application of fluorovinylic polymers and surface modification of conventional polyolefinic microporous membrans we being continuously tried.

• Carbon letters
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• v.15 no.3
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• pp.210-213
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• 2014

Nitrogen-doped microporous carbons were prepared using a polyvinylidene fluoride/melamine mixture. The electrochemical performance of the nitrogen-doped microporous carbons after being subjected to different carbonization conditions was investigated. The nitrogen to carbon ratio and specific surface area decreased with an increase in the carbonization temperature. However, the maximum specific capacitance of 208 F/g was obtained at a carbonization temperature of $800^{\circ}C$ because it produced the highest microporosity.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.89-89
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• 2006

• Macromolecular Research
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• v.14 no.1
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• pp.52-58
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• 2006

A novel fabrication of the patterned surfaces in the polymer films was demonstrated by using the self-organizing character of the block copolymers of polystyrene-b-oligothiophenes and polystyrene-b-aromatic amide dendron. Hexagonally arranged open pores with a micrometer-size were spontaneously formed by casting the polymer solutions under a moist air flow. The amphiphilic character of the block copolymers played the crucial role as a surfactant to stabilize the inverse emulsion of water in the organic solvent, and subsequently the aggregated structure of the hydrophilic oligothiophene or aromatic amide dendron segments remained on the interiors of the micropores. The chemical composition on the top of the surface of the microporous films was characterized by energy-filtering transmission electron microscopy (EFTEM) or a time-of-flight secondary ion mass spectrometer (ToF-SIMS). The characterizations clearly indicated that the patterned surfaces in the self-organized block copolymer films with the hexagonally ordered microporous structures were fabricated in a single step.

• Membrane Journal
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• v.7 no.1
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• pp.1-10
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• 1997

A review is presented for various gas transport mechanisms through microporous membranes of both polymeric and inorganic materials. Different transport modes manifest depending on the pore size and the flow regime, which is a function of pressure, temperature, and the interaction between gas molecules and the pore walls. For microporous membranes whose pores are small and the internal surface area huge, the surface diffusion becomes a significant factor. If the pores become even smaller, then the transport mechanism will be more of an activated diffusion type. When conditions are right capillary condensation will take place to create an enormous capillary pressure gradient, which will greatly enhance the permeation flux. At the same time the capillary condensate of the heavier component may block the membrane pores denying the passage of the lighter gas molecules. All of these phenomena will influence the separation of mixtures.