Perfluorinated sulfonic acid ionomers have been used as representative membrane materials in a wide range of applications. Though PFSA ionomers have been well known as chemically durable materials, their chemical resistances should be improved further to apply them to practical fuel cell systems operated under harsh conditions. One plausible solution would be to fabricate reinforced membranes composed of proton-conducting ionomers and chemically durable porous support films. In this study, pore-filling membranes are prepared via the impregnation of PFSA ionomers into porous PTFE support films. The objective of this study is to systematically investigate the influences of pore characteristics on proton transport behavior and electrochemical single performances.

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.

Porous W with controlled pore structure was fabricated by thermal decomposition and hydrogen reduction process of PMMA beads and WO3 powder compacts. The PMMA sizes of 8 and 50 μm were used as pore forming agent for fabricating the porous W. The WO3 powder compacts with 20 and 70 vol% PMMA were prepared by uniaxial pressing and sintered for 2 h at 1200oC in hydrogen atmosphere. TGA analysis revealed that the PMMA was decomposed at about 400oC and WO3 was reduced to metallic W at 800oC. Large pores in the sintered specimens were formed by thermal decomposition of spherical PMMA, and their size was increased with increase in PMMA size and the amount of PMMA addition. Also the pore shape was changed from spherical to irregular form with increasing PMMA contents due to the agglomeration of PMMA in the powder mixing process.

Ceramics biomaterials are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/β-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/β-TCP powders with 10-30 wt% NH4HCO3 as a space holder(SH) and TiH2 as a foaming agent, and MgO powder as a binder. The HA/β-TCP powders were consolidated by spark plasma sintering(SPS) process at 1000 oC under 20 MPa conditions. The effect of SH content on the pore size and distribution of the HA/β-TCP composite was observed by scanning electron microscopy(SEM) and a microfocus X-ray computer tomography system(SMX-225CT). These microstructure observations revealed that the volume fraction of the pores increased with increasing SH content. The pore size of the HA/β-TCP composites is about 400-500 μm. The relative density of the porous HA/β-TCP composite increased with decreasing SH content. The porous HA/β-TCP composite fabricated with 30%SH exhibited an elastic modulus similar to that of cortical bone; however, the compression strength of this composite is higher than that of cortical bone.

This paper proposes a novel way of fabricating aligned porous Sn by freeze-drying of camphene slurry with stannic oxide (SnO2) coated Sn powders. The SnO2 coated Sn powders were prepared by surface oxidation of the initial and ball-milled Sn powders, as well as heat treatment of tin chloride coated Cu powders. Camphene slurries with 10 vol% solid powders were prepared by mixing at 50 oC with a small amount of oligomeric polyester dispersant. Freezing the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled at −25 oC. Improved dispersion stability of camphene slurry and the homogeneous frozen body was achieved using the oxidized Sn powder at 670 oC in air after ball milling. The porous Sn specimen, prepared by freeze-drying of the camphene slurry with oxidized Sn powder from the heat-treated Sn/tin chloride mixture and sintering at 1100 oC for 1 h in a hydrogen atmosphere, showed large pores of about 200 μm, which were aligned parallel to the camphene growth direction, and small pores in their internal walls. However, 100 μm spherical particles were observed in the bottom part of the specimen due to the melting of the Sn powder during sintering of the green compact.

The existing metal getters are invariably covered with thin oxide layers in air and the native oxide layer must be dissolved into the getter materials for activation. However, high temperature is needed for the activation, which leads to unavoidable deleterious effects on the devices. Therefore, to improve the device efficiency and gas-adsorption properties of the device, it is essential to synthesize the getter with a method that does not require a thermal activation temperature. In this study, getter material was synthesized using palladium oxide (PdOx) which can adsorb H2 gas. To enhance the efficiency of the hydrogen and moisture absorption, a porous layer with a large specific area was fabricated by an etching process and used as supporting substrates. It was confirmed that the moisture-absorption performance of the SiO2/Si was characterized by water vapor volume with relative humidity. The gas-adsorption properties occurred in the absence of the activation process.

The present study demonstrates the effect of solidification condition on the pore structure in freeze drying process using the slurries of CuOlimable vehicles. Camphene and Camphor-45 wt% naphthalene based slurries with 14 vol% CuO powder were frozen into a mold at -25℃<, followed by sublimation at room temperature. The green bodies were hydrogen-reduced and sintered at 500℃ for 1 h. The porous Cu specimen, frozen the CuO/camphene slurry into the heated mold of the upper part, showed large pores with unidirectional pore channels and small pores in their internal wall. Also, it was observed that the size of large pores was decreasing near the bottom part of specimen. The change of pore structure depending on the freezing condition was explained by the nucleation behavior of camphene crystals and rearrangement of solid powders during solidification. In case of porous Cu prepared from CuO/Camphor-naphthalene system, the pore structure exhibited plate shape as a replica of the original structure of crystallized vehicles with hypereutectic composition.

Metal foams have a cellular structure consisting of a solid metal containing a large volume fraction ofpores. In particular, open, penetrating pores are necessary for industrial applications such as in high temperature filtersand as a support for catalysts. In this study, Fe foam with above 90% porosity and 2 millimeter pore size was suc-cessfully fabricated by a slurry coating process and the pore properties were characterized. The Fe and Fe2O3 powdermixing ratios were controlled to produce Fe foams with different pore size and porosity. First, the slurry was preparedby uniform mixing with powders, distilled water and polyvinyl alcohol(PVA). After slurry coating on the polyure-thane(PU) foam, the sample was dried at 80℃. The PVA and PU foams were then removed by heating at 700℃ for 3hours. The debinded samples were subsequently sintered at 1250℃ with a holding time of 3 hours under hydrogenatmosphere. The three dimensional geometries of the obtained Fe foams with an open cell structure were investigatedusing X-ray micro CT(computed tomography) as well as the pore morphology, size and phase. The coated amount ofslurry on the PU foam were increased with Fe2O3 mixing powder ratio but the shrinkage and porosity of Fe foams weredecreased with Fe2O3 mixing powder ratio.

본 연구에서는 졸-겔, 용매치환, 표면개질, 상압건조 공정과 계면활성제에 의한 템플레이팅(templating) 공법 및 소결 공정을 이용하여 실리카 에어로겔 모노리스와 메조포러스 실리카 모노리스를 각각 합성하였다. 제조된 두 종류의 실리카 모노리스는 균열이 없이 비교적 투명하였으며, 매우 높은 기공율(92-94%) 및 비표면적(800 - 840 m²/g)과 수 십 nm 수준의 기공 크기를 갖는 것으로 확인되었다. 표면개질을 적용한 실리카 에어로겔 샘플이 스피링백 효과로 인하여 메조포러스 실리카 모노리스에 비해 더욱 미세하고 균질한 나노 기공 구조를 보였을 뿐만 아니라, 그 단열 성능도 더욱 우수한 것으로 나타났다. 본 연구를 통해 합성된 두 종류의 실리카 모노리스를 중간층으로 적용한 복층 창유리의 단열성능을 측정된 모노리스의 열전도도와 이론식을 근거로 조사한 결과, 기존의 상업적으로 응용되는 공기층 삽입 복층 창유리에 비해 우수한 단열 성능을 보이는 것으로 나타났다.

A numerical analysis was performed to study PEMFC performance characteristics depending on the flow direction of cathode reactant gas, cathode relative humidity, and porosity of gas diffusion layer. As cathode relative humidity decreases and porosity increases, current density increases due to better diffusion of reactant gas to cathode surface. As current density increases, power density increases initially and then decreases with its maximum located around current density value of 2.2 Amperes per square centimeter. From the analysis of current density distribution inside membrane, the counter-flow cases show more uniform profile across the membrane than the co-flow cases due to more uniform reactant gas supply.

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-finefecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid(0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing andsintering processes were conduced. In order to examine the effect of cell size (200 µm, 450 µm, 500 µm) in process,pre-samples were sintered for two hours at temperature of 1450˚C, in H₂ atmospheres. A 24-hour thermo gravimetricanalysis test was conducted at 1000˚C in a 79% N₂ + 21% O₂ to investigate the high temperature oxidation behavior ofpowder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased withincreasing cell size. In the 200 µm porous metal with a thinner strut and larger specific surface area, the depletion ofthe stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared withthe 450, 500 µm porous metals.

Fe foam with above 90% porosity and 2 millimeter pore size was successfully fabricated by a slurry coating process. In this study, the binder contents were controlled to produce the Fe foam with different pore size, strut thickness and porosity. Firstly, the slurry was prepared by uniform mixing with Fe powders, distilled water and polyvinyl alcohol(PVA) as initial materials. After slurry coating on the polyurethane(PU) foam the sample was dried at 80oC. The PVA and PU foams were then removed by heating at 700oC for 3 hours. The debinded samples were subsequently sintered at 1250oC with holding time of 3 hours under hydrogen atmosphere. The three dimensional geometries of the obtained Fe foams with open cell structure were investigated using X-ray micro CT(computed tomography) as well as the pore morphology, size and phase.

본 연구에서는 아세틸화된 메틸 셀룰로스를 복합박막 정삼투막의 지지층으로 사용하였다. 계면중합법을 이용하여 선택성이 우수한 폴리아미드 활성층을 다양한 지지층 위에 코팅하였다. 아세틸화된 메틸 셀룰로스 지지층 위에 코팅된 복합 박막 정삼투막의 구조와 성능을 다른 지지층 위에 코팅된 복합박막 정삼투막과 비교하였다. 실험적 결과는 아세틸화된 메틸 셀룰로스 지지층 위에 코팅된 복합박막 정삼투막의 성능이 다른 정삼투막들에 비해서 우수하였으며 이것은 구조적인 특성과 염의 낮은 역확산속도 때문인 것으로 사료된다.

In this paper, a three dimensional numerical analysis tool was applied to study the PEMFC performance characteristics. The porosity and electrical conductivity of GDL and CL as well as the relative humidity of anode and cathode channel gas were selected as simulation parameters. The porosity of GDL and CL was varied as 0.3, 0.5, and 0.7. The relative humidity of anode and cathode was varied as 0, 20, 40, 60, 80, and 100 percent. The electrical conductivity of GDL and CL was varied as 1, 5, 10, 50, 102, and 104 1/Ω·m. For a constant cell voltage condition, the maximum current density was obtained at GDL porosity of 0.7, anode relative humidity of 100 percent, cathode relative humidity of 60 percent, and electrical conductivity of 104 1/Ω·m for GDL and CL. As the porosity of GDL and CL increases, current density increases because reactant gases diffuse well. As the electrical conductivity of GDL and CL increases, current density increases due to increased electron transfer rate. As anode relative humidity increases, current density increases. Unlike anode, current density increases when cathode relative humidity increases from 0 percent to 60 percent. Then current density decreases when cathode relative humidity increases from 60 percent to 100 percent.

A numerical analysis was performed to study PEMFC characteristics depending on GDL porosity and the inlet direction in cathode gas channel using the FLUENT. As GDL porosity increases, temperature increases. For the both of co-flow and counter-flow cases, temperature is higher near the hydrogen inlet region where the chemical reaction rate is high. As GDL porosity increases, current density increases. In overall, counter-flow case gives higher current density compared to co-flow case for the same operating conditions. However, the difference in the current density is not high. The water mass fraction is also higher near the hydrogen inlet region due to the chemical reaction rate for the both of co-flow and counter-flow cases.

Today, the modification of carbon foam for high performance remains a major issue in the environment and energy industries. One promising way to solve this problem is the optimization of the pore structure for desired properties as well as for efficient performance. In this study, using a sol-gel process followed by carbonization in an inert atmosphere, hollow spherical carbon foam was prepared using resorcinol and formaldehyde precursors catalyzed by 4-aminobenzoic acid; the effect of carbonization temperature and re-immersion treatment on the pore structure and characteristics of the hollow spherical carbon foam was investigated. As the carbonization temperature increased, the porosity and average pore diameter were found to decrease but the compression strength and electrical conductivity dramatically increased in the temperature range of this study (700˚C to 850˚C). The significant differences of X-ray diffraction patterns obtained from the carbon foams carbonized under different temperatures implied that the degree of crystallinity greatly affects the characteristics of the carbon form. Also, the number of re-impregnations of carbon form in the resorcinol-formaldehyde resin was varied from 1 to 10 times, followed by re-carbonization at 800˚C for 2 hours under argon gas flow. As the number of re-immersion treatments increased, the porosity decreased while the compression strength improved by about four times when re-impregnation was repeated 10 times. These results imply the possibility of customizing the characteristics of carbon foam by controlling the carbonization and re-immersion conditions.

본 연구에서는 용매열합성법(solvothermal method)을 이용해 나노기공 HKUST-1 분리막을 제조하였다. In-situ 용매열합성법을 이용하는 경우, 매크로 기공의 알루미나 지지체 위에 균일하고 균열이 없는 HKUST-1 층을 형성하기 어렵다. 본 연구에서는 용매열합성 전에 알루미나 지지체의 표면을 가열한 상태에서 용매열합성의 전구체 용액을 분무하므로 연속적이고 균열이 없는 HKUST-1 분리막을 제조할 수 있었다. 합성된 HKUST-1 분리막은 XRD, FE-SEM 및 단일 기체투과 실험 등을 통해 분석하였다.

In this paper, the PEMFC performance was studied using three dimensional numerical analysis. The effect of GDL porosity and cathode inlet humidity on the cell polarization curve was analyzed. The GDL porosity of 0.3, 0.5, 0.7 and cathode inlet humidity of 20, 40, 60, 80, 100 percent were selected as simulation cases while the anode inlet humidity was maintained as 100 percent. For a constant cell voltage condition, the highest current density was obtained at GDL porosity of 0.7 and cathode inlet humidity of 20 percent. As GDL porosity increases, the amount of hydrogen diffusion to membrane from the anode increases and chemical reaction also increases. As cathode inlet humidity decreases, oxygen mass fraction of cathode gas channel increases and chemical reaction also increases.

The purpose of our study was to develop the fabrication method of porous diatomite ceramics with a porosity gradient by centrifugal molding. The processing variables of centrifugal molding were derived from Stoke's law of sedimentation, which were the radius of the particles, the acceleration due to centrifugal molding and the dynamic viscosity of the slurry. And these could be controlled by ball-milling conditions, centrifugal conditions, and the addition of methyl cellulose, respectively. The effects of processing conditions on the gradient pore structure of diatomite were investigated by particle size analysis, scanning electron microscope, and mercury porosimeter.