The effect of tert-butyl alcohol (TBA) as a freezing solvent on the pore structure of a porous tungsten body prepared by freeze-drying is analyzed. TBA slurries with a WO3 content of 10 vol% are prepared by mixing with a small amount of dispersant and binder at 30oC. The slurries are frozen at -25oC, and pores are formed in the frozen specimens by the sublimation of TBA during drying in air. After hydrogen reduction at 800oC and sintering at 1000oC, the green body of WO3 is completely converted to porous W with various pore structures. Directional pores from the center of the specimen to the outside are observed in the sintered bodies because of the columnar growth of TBA. A decrease in pore directionality and porosity is observed in the specimens prepared by long-duration drying and sintering. The change in pore structure is explained by the growth of the freezing solvent and densification.

The effect of sublimable vehicles on the pore structure of Cu fabricated by freeze drying is investigated. The 5 vol% CuO-dispersed slurries with camphene and various camphor-naphthalene compositions are frozen in a Teflon mold at -25oC, followed by sublimation at room temperature. After hydrogen reduction at 300oC and sintering at 600 °C, the green bodies of CuO are completely converted to Cu with various pore structures. The sintered samples prepared using CuO/camphene slurries show large pores that are aligned parallel to the sublimable vehicle growth direction. In addition, a dense microstructure is observed in the bottom section of the specimen where the solidification heat was released, owing to the difference in the solidification behavior of the camphene crystals. The porous Cu shows different pore structures, such as dendritic, rod-like, and plate shaped, depending on the composition of the camphornaphthalene system. The change in pore structure is explained by the crystal growth behavior of primary camphor and eutectic and primary naphthalene. Keywords: Porous Cu, Pore structure

In order to develop a process for manufacturing a composite structure of an intermetallic compound foam and a hollow material, the firing and pore form of the Al-Ni precursor in a steel pipe are investigated. When the Al-Ni precursor is foamed in a hollow pipe, if the temperature distribution inside the precursor is uneven, the pore shape distribution becomes uneven. In free foaming, no anisotropy is observed in the foaming direction and the pore shape is isotropic. However, in the hollow pipe, the pipe expands in the pipe axis direction and fills the pipe. The interfacial adhesion between Al3Ni foam and steel pipe is excellent, and interfacial pore and reaction layer are not observed by SEM. In free foaming, the porosity is 90 %, but it decreases to about 80 % in the foam in the pipe. In the pipe foaming, most of the pore shape appears elongated in the pipe direction in the vicinity of the pipe, and this tendency is more remarkable when the inside pipe diameter is small. It can be seen that the pore size of the foam sample in the pipe is larger than that of free foam, because coarse pores remain after solidification of the foam because the shape of the foam is supported by the pipe. The vertical/horizontal length ratio expands along the pipe axis direction by foaming in the pipe, and therefore circularity is reduced.

Chlorella-derived activated carbon (CDAC) with a high specific surface area and hierarchical pore structure was prepared as a CO2 adsorbent and as a supercapacitor electrode material. During KOH activation of Chlorella-derived carbon, metallic K gas penetrated from the outer walls to the inner cells, and pores formed on the outer frame and the inner surface. Micropores were dominant in CDAC, contributing toward a high specific surface area (> 3500 m2/g) and a hierarchical pore structure owing to the cell walls. Consequently, CDAC exhibited a high CO2 adsorption capacity (13.41 mmol/g at 10 atm and room temperature) and afforded high specific capacitance (142 F/g) and rate capability (retention ratio: 91.5%) in supercapacitors. Compared with woody- and herbaceous-biomass-derived activated carbons, CDAC has a superior specific surface area when the precursors are used without any pretreatment under the same conditions due to their soft components such as lipids and proteins. Furthermore, developing microalgae into high-value-added products is beneficial from both economic and environmental perspectives.

We fabricated a Li-S battery with post-treated carbon nanotube (CNT) films which offered better support for sulfur, and investigated the effect of the surface properties and pore structure of the post-treated CNT films on Li-S battery performance. Post-treatments, i.e., acid treatment, unzip process and cetyltrimethylammonium bromide (CTAB) treatment, effectively modified the surface properties and pore structure of the CNT film. The modified pore structure impacted the ability of the CNT films to accommodate the catholyte, resulting in an increase in initial discharge capacity.

Various carbon aerogels (CAs) were prepared from polymerization of resorcinol and formaldehyde and applied as the electrode materials of an electric double layer capacitor (EDLC) with the aim of controlling the textural and electrochemical properties of CAs by the type of base catalyst and the ratio of resorcinol to catalyst (R/C). The CAs from NaHCO3 and KHCO3 with H+ ions had higher specific surface areas but exhibited lower electrochemical properties than those from K2CO3 and Na2CO3, which had more uniform pore size distributions. The electrochemical properties of Na2CO3 were superior to those of K2CO3 probably because the polarizing power of Na+ ions was higher than K+ ions. With an increasing R/C ratio, the pore sizes of CA showed a tendency to increase but the uniformity of the pore size distribution got worse. For the four base catalysts, the highest electrochemical property was obtained at the R/C ratio of 500.

수분을 포함한 압축공기는 공압 시스템에서 부식과 관석 등의 여러가지 문 제를 유발하기 때문에 기상 내의 수분을 효율적으로 제거하기 위한 다양한 기술이 개발되어오고 있다. 특히, 분리막을 이용한 제습 방법은 에너지 소비가 작 고, 장치를 소형화할 수 있다는 장점으로 주목받고 있다. 본 연구에서는 제습용 중공사막을 상전이 방적법으로 제조하고, 친수성 또는 소수성으로 표면 개질하였다. 선택도와 투과도 향상을 위하여 기공 구조를 제어하였으며, SEM, 기체 투 과도, 접촉각 측정 등으로 중공사막의 특성을 분석하였다. 또한, 분리막을 모듈 화하여 제습 실험을 수행하였으며, 여러 운전 조건에서의 특성을 확인하였다.

본 연구에서는 입자크기가 다른 3가지 α-알루미나 분체로부터 주입성형법과 소결법을 혼용하여 튜브형 α-알루 미나 지지체를 제조하여 초기 α-알루미나 분체의 입자크기와 소결 온도가 지지체의 기공구조와 기체투과 특성에 미치는 영 향을 고찰하였다. 평균입경이 0.2, 0.5, 1.7 μm인 α-알루미나 분체를 사용했을 시 제조된 α-알루미나 지지체는 각각 약 80, 130, 200 nm의 평균 기공경을 가졌으며 평균 기공경은 소결 온도 보다는 초기 알루미나 분체의 입자크기에 의존하였다. 모 든 시편에서 소결 온도가 증가할수록 지지체의 부피 밀도는 증가하였고 겉보기 기공률은 감소하였다. He, N2, O2, CO2에 대 하여 30°C에서 단일기체 투과 특성을 평가한 결과, 기체 투과도는 기공경 제곱에 비례하여 증가하였고 기공률이 증가함에 따 라서 직선적으로 증가하였다. 이를 토대로 제조된 α-알루미나 지지체의 기체 투과는 점성유동(viscous flow)에 의하여 이루 어지며, α-알루미나 지지체의 기체 투과 특성은 초기 α-알루미나 분체의 입자크기와 소결온도를 제어함으로써 조절될 수 있 음을 확인할 수 있었다.

본 연구에서는 입자크기가 다른 3가지 α-알루미나 분말로 부터 주입성형법과 소결법을 혼용하여 튜브형 α-알루미나 지지체 제작하였고 이때에 초기 α-알루 미나 분말의 입자크기와 소결 온도가 지지체의 기공구조와 기공구조가 투과 특 성에 미치는 영향을 고찰하였다. 제작 된 지지체는 수은함침법과 Archimedes 법을 통하여 기공경과 기공률을 측정하였다. 또한 30°C에서 He, N2, O2, CO2 기체에 대하여 투과 특성을 고찰하여, 각 지지체의 토튜오서티를 계산 하였으며, 지지체의 기공경 및 기공률이 지지체의 기체 투과 특성에 미치는 영향을 고찰 하였다.

제올라이트 분리막은 미세기공이 결정구조에서 비롯되기 때문에 매우 좁고 균일한 미세기공 구조를 갖는 것으로 알려져 있다. 따라서 다공성 지지체 표면에 결함이 없는 균일한 제올라이트 분리층을 안정적으로 형성하기 위한 연구는 매우 중요한 부분이다. 본 연구에서는 다공성 알루미나 지지체 표면에 물/알코올 분리성능이 우수한 투과증발용 NaA, CHA 제올라이트 분리막을 형성시키기 위하여 50-100 nm 크기의 종결정을 도입한 후 수열합성법으로 이차성장시켜 분리막을 제조하였다. 그리고 분리층에 존재하는 비 제올라이트 기공구조(non-zeolitic pore structure)를 상세하게 분석하기 위하여 H2,N2,SF6 등의 단일 가스 투과 거동을 분석함으로써 비제올라이트 기공의 크기를 예측하고자 하였다.

Ultrafiltration membranes are capable of acting as barriers to bacteria, viruses, spores, pollens, colloidal suspensions, high molecular weight solutes, pathogens and pesticides. Pore structure characterization of these include through pore throat diameter, bubble point pore diameter, mean flow pore diameter, pore distribution and liquid permeability. Liquid Liquid Porometery is a novel technique for measuring pores in the Ultrafiltration range without any damage or rupture to the membrane. Liquid Liquid Porometer uses two immiscible & saturated wetting liquids. Pores are filled with first liquid and second liquid is pressurized to displace the first liquid and flow through the pores. The amount of liquid flowing out is measured. Second liquid flow rate and differential pressure are measured. Pore distributions are computed like those in Capillary Flow Porometer.

The present study demonstrates the effect of freezing conditions on the pore structure of porous Cu-10 wt.% Sn prepared by freeze drying of CuO-SnO2/camphene slurry. Mixtures of CuO and SnO2 powders are prepared by ball milling for 10 h. Camphene slurries with 10 vol.% of CuO-SnO2 are unidirectionally frozen in a mold maintained at a temperature of -30oC for 1 and 24 h, respectively. Pores are generated by the sublimation of camphene at room temperature. After hydrogen reduction and sintering at 650oC for 2 h, the green body of the CuO-SnO2 is completely converted into porous Cu-Sn alloy. Microstructural observation reveals that the sintered samples have large pores which are aligned parallel to the camphene growth direction. The size of the large pores increases from 150 to 300 μm with an increase in the holding time. Also, the internal walls of the large pores contain relatively small pores whose size increases with the holding time. The change in pore structure is explained by the growth behavior of the camphene crystals and rearrangement of the solid particles during the freezing process.

본 연구에서는 평균입경 0.2, 0.5, 1,7㎛ 크기의 α-알루미나 분말을 이용하여 다공성 α-알루미나 지지체의 기공구조를 조절하고자 하였다. 다공성 α-알루미나 지지체는 슬립캐스팅공법을 이용하여 제조한 후 소결하였으며, 이 때 소결 온도가 지지체의 기공특성에 미치는 영향에 대하여 고찰하였다. 제조된 다공성 α-알루미나 지지체는 수은기공분석기를 이용하여 기공크기 및 기공률 등을 분석하였으며, 단일기체투과장치를 이용하여 기체 투과도를 측정하였다. 그 결과 평균입경 0.2, 0.5, 1.7㎛ 크기의 α-알루미나 분말을 이용하여 제조된 지지체는 각각 80, 130, 200㎚의 기공경을 가졌으며, CO2 단일기체에 대해 각각 1300, 1700, 5000GPU를 나타냈다.

The effect of sublimable vehicle composition in the camphor-naphthalene system on the pore structure ofporous Cu-Ni alloy is investigated. The CuO-NiO mixed slurries with hypoeutectic, eutectic and hypereutectic compo-sitions are frozen into a mold at -25oC. Pores are generated by sublimation of the vehicles at room temperature. Afterhydrogen reduction at 300oC and sintering at 850oC for 1 h, the green body of CuO-NiO is completely converted toporous Cu-Ni alloy with various pore structures. The sintered samples show large pores which are aligned parallel to thesublimable vehicle growth direction. The pore size and porosity decrease with increase in powder content due to thedegree of powder rearrangement in slurry. In the hypoeutectic composition slurry, small pores with dendritic morphologyare observed in the sintered Cu-Ni, whereas the specimen of hypereutectic composition shows pore structure of plateshape. The change of pore structure is explained by growth behavior of primary camphor and naphthalene crystals dur-ing solidification of camphor-naphthalene alloys.

본 연구에서는 평균입경 0.2, 0.5㎛ 크기의 α-알루미나 분말을 이용하여 다공성 α-알루미나 지지체의 기공구조를 조절하고자 하였다. 다공성 α-알루미나 지지체는 슬립캐스팅공법을 이용하여 제조한 후 소결하였으며, 이 때 소결 온도가 지지체의 수축률 및 소결거동 등에 미치는 영향에 대하여 고찰하였다. 제조된 다공성 α-알루미나 지지체는 수은기공분석기를 이용하여 기공크기 및 기공률 등을 분석하였으며, 단일기체투과장치를 이용하여 기체 투과도를 측정하였다. 그 결과 평균입경 0.5㎛ 크기의 α-알루미나 분말을 이용하여 제조된 지지체의 경우, 평균 입경 0.2㎛ 크기의 α-알루미나 분말을 이용하여 제조된 지지체에 비하여 기공크기가 크고 기공률이 높았으며, 기체투과도가 높을 것을 알 수 있었다.

PURPOSES : In this study, an image analysis method is used to evaluate the pore structure characteristics and permeability of hybrid concrete. METHODS: The binder weight of hybrid concrete is set to 400 kg/m3, 370kg/m3, and 350 kg/m3, and for each value of binder weight, the pore structure and permeability of concrete mixture is evaluated. The permeability of hybrid concrete is evaluated using a rapid chloride penetration test(RCPT). RESULTS : The concrete pore structure characteristics of hybrid concrete reveals that as the binder weight is reduced, the entrained air is reduced and the entrapped air is increased. The permeability of the hybrid concrete for all values was measured to be below 1000 C, which indicates a "Very Low" level of permeability relative to the evaluation standard of KS F 2711. Additionally, as the binder weight is decreased, there is a significant increase in the permeability of chloride ions. CONCLUSIONS : In this study, the pore structure characteristics of hybrid concrete at different binder weights shows that as the binder weight is reduced, the entrained air is reduced and the entrapped air is increased. Consequently, chloride ion penetration resistance of the hybrid concrete is diminished. As a result, it is expected that this will reduce the concrete’s durability.