• 한국세라믹학회지
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• 제41권7호
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• pp.560-566
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• 2004

다중 압출 공정을 이용하여 알루미나 연속다공질체를 제조하기 위해 기공형성제로서 탄소 분말을 사용하였으며 세라믹 분말의 성형을 용이하게 하기 위하여 에틸렌 비닐 아세테이트 고분자를 바인더로 사용하였다. 압출 횟수, 압출비 및 재료의 부피비를 제어함으로써 균일한 기공의 크기와 기공률을 용이하게 제어하였다. 제조된 소결체는 연속기공을 가질 뿐아니라 우수한 비표면적을 가졌으며, 기존의 공정에 의해 제조된 알루미나 다공질 재료보다 우수한 곡강도 값을 보였다. 생체 친화성 평가를 위해 인간의 뼈모세포인 MG-63 세포를 이용해 In-vitro 실험을 실시한 결과 기공의 아랫면, 윗면, 내부 및 외부에 세포가 잘 생착하여 네트워크 형태로 치밀하게 잘 성장하였다. 또한 이 재료를 이용하여 3차원 다공질체로 제조한 후 생체적합성을 평가하기 위해 쥐의 피하조직에 이식한 결과 어떠한 염증 소견이나 생체 거부반응이 없었으며 섬유조직으로 잘 둘러 쌓인 다공질체 주위로 새로운 모세혈관이 활발히 생성되었다.

• 한국세라믹학회지
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• 제54권4호
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• pp.331-339
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• 2017

Porous alumina-based ceramics are of special interest due to their outstanding mechanical properties and their thermal and chemical stability. Nevertheless, the high electrical resistance of alumina-based ceramics, due to the generation of static electricity, leads to difficulty in applying a vacuum chuck in the semi-conductor process. Therefore, development of alumina-based ceramics for applications with vacuum chucks aims to have primary properties of low electrical resistance and high air permeability. In this study, we tailored the electrical resistance of porous alumina-based ceramics by adjusting the amount of $MnO_2$ (with $TiO_2$ fixed at an amount of 2 wt%) and by using coarse alumina powder for high air permeability. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimeter, capillary flow porosimetry, universal testing machine, X-ray diffraction and high-resistance meter.

• 한국세라믹학회지
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• 제46권6호
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• pp.609-614
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• 2009

The low-temperature preparation of porous ceramics was carried out using mixtures of alumina-zinc borosilicate (ZBS) glass. The compositions of alumina-ZBS glass mixture with PMMA pore-former were unfortunately densified. Because PMMA was evaporated below the softening point of ZBS glass ($588{^{\circ}C}$), the densification through the pore-filling caused by the capillary force might occur. Howerver, those with carbon possessed pores where carbon was evaporated above the softening point. The porous ceramic having 35% porosity was successively fabricated by the low-temperature sintering process below $900{^{\circ}C}$ using 45 vol% of alumina, 45 vol% ZBS of glass, and 10 vol% of carbon as starting materials.

• Journal of the Korean Wood Science and Technology
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• 제46권6호
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• pp.681-691
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• 2018

The typical methods of mercury intrusion porosimetry (MIP) and capillary flow porometry (CFP) were used to evaluate the pore size of cross-section of wood and the effect of the pore structure on the permeability of wood was analyzed in this study. The results of this study were as followings: The pore size of wood measured by CFP was larger than that measured by MIP except for Lime tree, Korean red pine and Paulownia. Among the three pore types of porous materials defined by IUPAC (through pores, blind pores, and closed pores), only through pores are related to permit fluid flow. MIP measures the pore size of both through pores and blind pores, while CFP measures the pore size of only constricted through pores. Therefore, pore size measured by MIP was not related to gas permeability, however pore size measured by CFP had a proportional relationship with gas permeability.

• 대한토목학회논문집
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• 제14권5호
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• pp.1137-1143
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• 1994

비포화 흐름에서 모세관 이력현상의 영향을 살펴보기 위하여 선행강우가 존재하는 지표면 경계조건하에서 이력현상을 고려한 경우와 고려하지 않은 경우에 대하여 종속변수가 모세관 압력수두인 Richards식을 수치해석하여 습윤전선의 전진 경향, 함수량 재분포현상, 침투율, 누가침투량 등을 비교 검토하였다. 비포화 흐름을 해석할 때 모세관 이력현상의 영향은 무시되어질 수 없고, 보다 정확한 비포화흐름의 해석은 이력현상을 고려함으로써 얻어질 수 있다. 만약 비포화 흐름을 해석할 때 이력현상을 고려할 수 없다면, 주마름곡선보다 주젖음곡선을 사용하는 것이 바람직하다.

• 한국막학회:학술대회논문집
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• 한국막학회 2001년도 제14회 심포지엄 : 제2회 분리막 표준화(The 2nd Standardization of Membranes)
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• pp.39-50
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• 2001

The performance of membranes is governed their pore struture. Pore structures of porous materials can be determined by a number of techniques. However, The novel technique, capillary folw porometry has a number of advantages. In this technique, the sample is brought in contact with a liquid that fills the pores in the membrane spontaneously. Gas under pressure is used to force the liquid from the pores and increase gas flow. Gas flow rate measured as a function of gas pressure in wet and dry samples yield data on the largest pore size, the mean flow pore size, flow distribution and permeability. Pore characteristics of a number of membranes were measured using this technique. This technique did not require the use of any toxic material and the pressure employed was low. Capillary flow porometry is a suitable technique for measurement of the pore structure of many membranes.

• 한국세라믹학회지
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• 제36권9호
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• pp.991-996
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• 1999

Effect of solution property on the weight varation and microstructural change of film was studied by electrophoretic deposition in order to obtain a homogeneous and dense zirconia film. As a result of weight kinetics of film which obtained in alcohol or aqueous solution having different polarity experimental data showed large deviation from theoretical ones calculated by Zhang's kinetic model. It had been shown that the weight affecting factors was largely dependent on properties other than dielectric constant and viscosity of solvent zeta potential appiled field and time. In initial stage a main factor of the drastic weight increase was the capillary drag of porous substrate. The cause of weight decrease with time in aqueous solution after 300 s was attributed to the defect of film by sagging and electrolytic reaction. The electrolyte film which prepared in alcohol solution with good wetting for substrate had better homogeneous and dense microstructure than one in aqueous solution with high surface tension.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권2호
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• pp.99-106
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• 2005

Falling film heat transfer has been widely used in many applications in which heat and mass transfer occur simultaneously, such as evaporative coolers, cooling towers, absorption chillers, etc. In such cases, it is desirable that the falling film spreads widely on the surface to form a thin liquid film to enlarge contact surface and to reduce the thermal resistance across the film and/or the flow resistance to the vapor stream over the film. In this respect, hydrophilic treatment of the surface has been tried to improve the surface wettability by decreasing the contact angle between the liquid and the surface. However, the hydrophilic treatment was found not very effective to increase the surface wettedness of inclined surfaces, since the liquid flow forms rivulet patterns instead of a thin film as it flows down the inclined surface and accelerates gradually by the gravity. In this work, a novel method is suggested to improve the surface wettedness enormously. In this work, the surface is treated to have a thin hydrophilic porous layer on the surface. With this treatment, the liquid can spread widely on the surface by the capillary force resulting from the porous structure. In addition to this, the liquid can be held within the porous structure to improve surface wettedness regardless of the surface inclination. The experiment on the evaporative cooling of inclined surfaces has been conducted to verify the effectiveness of the surface treatment. It is measured that the latent heat transfer increases almost by $80\%$ at the hydrophilic porous layer coated surface as compared with the untreated surface.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.518-519
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• 2006

A connection between pulse-periodical laser radiation power and stability of liquid-metal contacts between powder particles during selective laser sintering (SLS) is determined based on analysis solving the problem of stability of liquid column in the gravity and capillary forces field. On the grounds of obtained relationships the optimization of pulse-periodical laser radiation power and SLS-process duration is realized, that allows to produce voluminous powder porous materials with pre-determined physical and mechanical properties and surface geometry. Results of metallographic investigations of powder porous materials of titanium powder produced with technological regimes calculated by means of obtained relationships are given in the work

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.636-643
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• 2024

The coolability of the debris bed with a simulant of solidified corium is experimentally studied, focusing on the effects of the structure of the axial stratified debris bed on the dryout heat flux (DHF). DHF was obtained for the four structures with different particle sizes for the axial stratified debris bed under top flooding. The experimental results show that the dryout position of the axial stratified debris bed is formed at the stratified interface indicated by the temperature rise, and the DHF of the axial stratified bed is much lower than that of the homogeneous bed packed with the upper small particles. To predict the dryout heat flux of the stratified debris beds, by considering the properties of the mixed area, a one-dimensional dryout heat flux model of the porous medium is derived from a water and vapor momentum equation for porous medium, two-phase permeability modifications, interfacial drag, and the correlation between capillary pressure and liquid saturation and verified with the experimental data. The modified model can give reasonable results under different structures.