• 한국분말재료학회지
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• 제22권2호
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• pp.100-104
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• 2015

The porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability. The Fe-Cr-Al alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. And then many researches are developed the Fe-Cr-Al porous metals for exhaust gas filter, hydrogen reformer catalyst support and chemical filter. In this study, the Fe-Cr-Al porous metals are developed with Fe-22Cr-6Al(wt) powder using powder compaction method. The mean size of Fe-22Cr-6Al(wt) powders is about $42.69{\mu}m$. In order to control pore size and porosity, Fe-Cr-Al powders are sintered at $1200{\sim}1450^{\circ}C$ and different sintering maintenance as 1~4 hours. The powders are pressed on disk shapes of 3 mm thickness using uniaxial press machine and sintered in high vacuum condition. The pore properties are evaluated using capillary flow porometer. As sintering temperature increased, relative density is increased from 73% to 96% and porosity, pore size are decreased from 27 to 3.3%, from 3.1 to $1.8{\mu}m$ respectively. When the sintering time is increased, the relative density is also increased from 76.5% to 84.7% and porosity, pore size are decreased from 23.5% to 15.3%, from 2.7 to $2.08{\mu}m$ respectively.

• 멤브레인
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• 제20권2호
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• pp.135-141
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• 2010

다양한 형태의 Polysulfone 막을 MBR공정에 적용하기 위해 제조하였다. 특히 제조공정에 있어서 여러 형태의 에테르형 알코올을 사용 도프용액에 첨가시킴으로써, 공경크기에 미치는 영향력을 조사하였다. 본 연구에서는 공경의 크기는 첨가된 첨가제의 끓는점에 의한 영향력보다는 그들 자체(첨가된 첨가제)의 분자구조에 의한 확산에 더 큰 영향력을 받고 있음을 보여주었다. 분자적으로 methoxy ($CH_3$-O-) < secondary propanol ($-CH_2$-CH(OH)$-CH_3$) < ethoxy ($CH_3-CH_2-O-$)의 순으로 공경크기가 커지고 그에 따라 순수투과도 또한 커짐을 보여주었다. 이러한 현상은 첨가된 용매가 분자적으로 ether형 알코올의 bulky한 정도에 따라 공경의 형성이 다른 형태로 나타나고 있음을 보여주고 있다. 본 연구에서는 다양한 형태의 ether형 alcohol를 통하여 바라고자하는 형태(평균 pore size 0.1~0.4 ${\mu}m$)의 MF (microfiltration)막을 제조할 수 있었으며, MBR (membrane bio-reactor)에 적용한 결과 2달 동안 안정되게 운전되었다.

• 한국세라믹학회지
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• 제41권1호
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• pp.62-68
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• 2004

본 연구에서는 SHS 공정에 의하여 기공의 크기를 조절함으로서 전기저항 발열 특성을 가지는 다공성 $MoSi_2$를 제조하는 공정에 관하여 연구하였다. 결함이 억제된 다공질 재료를 제조하기 위하여 Si 함량 변화 및 예열 공정을 실시하였으며, 성형체 제조에 사용되는 Mo 분말의 크기 변화에 따른 가공 형성 거동에 대하여 연구하였다. 실험 결과 합성된 $MoSi_2$ 입자의 크기는 Mo 입자의 크기와는 관계없이 연소 합성시 발열되는 발열양에 의해 좌우되었으며, 기공의 크기는 Mo 입자의 크기에 따라 결정되었다. 또한 가공 경사 $MoSi_2$ 다공질 재료를 만들기 위하여 150-300${\mu}m$ Mo 분말과 4-5${\mu}m$ Mo 분말을 단계별로 5층으로 혼합하여 합성한 결과 거시적으로 순차적인 기공 크기 분포를 나타내었으며, 이를 통하여 포집 효율등이 우수한 다공성 발열체 재료의 제조가 가능하였다.

• 한국세라믹학회지
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• 제44권6호
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• pp.325-330
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• 2007

High porous AlO(OH) gel is used in precursor of ceramic material, coating material and porous catalyst. For use of these, not only physiochemical control for particle morphology, pore characteristic and peptization but also studies of synthetic method for preparation of high porous AlO(OH) gel were required. In this study, high porous AlO(OH) gel was prepared through the aging and filtration process of aluminum hydroxides gel precipitated by the hydrolysis reaction of $Na_2CO_3$ solution and $Al_2(SO_4)_3$ and $Na_2SO_4$ mixed solution. In this process, optimum synthetic condition of AlO(OH) gel having excellent pore volume as studying the effect of hydrolysis pH on gel precipitates has been studied. Hydrolysis pH brought about numerous changes on crystal morphology, surface area, pore volume and pore size. Physiochemical properties of gel were investigated as using XRD, TEM, TG/DTA, FT-IR and $N_2$ BET method.

• 한국세라믹학회지
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• 제44권12호
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• pp.727-732
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• 2007

In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

• 콘크리트학회논문집
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• 제21권2호
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• pp.147-152
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• 2009

본 연구는 국내에서 최초로 개발된 폐유리로 제조된 인공경량골재 (artifical lightweight aggregate: ALA)의 물리적 특성에 관한 연구를 통해 경량 모르타르 및 경량 콘크리트의 개발에 기초자료로 활용하기 위해 인공경량골재의 입도에 따른 3종류 (La, Lb, Lc)의 모르타르에 대하여 압축강도 실험, 단위질량 및 모르타르의 흡수율 실험을 실시하였다. 이상의 실험 결과, ALA의 밀도 및 단위질량은 내부의 독립기공구조로 인하여 보통골재의 50% 이하의 값을 나타냈으며, ALA를 사용한 모르타르의 흡수율시험 결과 Control 모르타르와 큰 차이가 없었다. 이는 ALA의 내부의 독립기공구조에 의한 것으로 판단된다. ALA를 사용한 모르타르의 경우 혼입률이 증가 할수록 압축강도와 휨강도는 감소하는 경향이 나타났으나, La50 모르타르를 제외한 모든 모르타르는 Control 모르타르 압축강도의 70% 이상을 나타내었다. 향후 광물질 혼화재, 물-시멘트비 의 조절에 따라 Control 모르타르와 동등한 강도가 발현 될 것이라 판단되며, 장기 내구성에 대한 검토도 함께 이루어져야 할 것으로 판단된다.

• 한국환경복원기술학회지
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• 제13권2호
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• pp.105-113
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• 2010

To investigate the restoration procedure on soil physical properties at the surface of visiting road affected by rest-year system. This study was carried out at visiting roads of stream of Chilsun in Jirisan. Mean soil strength in 20cm of soil depth was lower in the Rest-Year System areas (1.5-1.9 times in Site 2, 1.1-7.5 times in Site 3) than in the control (Site 1). Soil strength was recovered by the Rest-Year System in the national park. Mesopore rate (pF 2.7) in 0-15 cm of soil depth was higher in the Rest-Year System areas (1.2 times) than in the control. This indicates that mesopore rate is rapidly restoring in the Rest-Year System areas. Pore space rate in 0-7.5 cm of soil depth was higher in the Rest-Year System areas (23.2% in Site 2, 23.6% in Site 3) than in the control (22.4% in Site 1). Pore space rate in 7.5-15 cm of soil depth was also higher in the Rest-Year System areas (22.9% in Site 2 and Site 3) than in the control (18.9% in Site 1). Soil pore space was remediable by the Rest-Year System. Bulk density in 0-7.5 cm of soil depth was lower in the Rest-Year System areas (1.674g/$cm^3$ in Site 2, 1.668g/$cm^3$ in Site 3) than in the control (1.723g/$cm^3$ in Site 1). Bulk density in 7.5-15 cm of soil depth was lower in the Rest-Year System areas (1.785g/$cm^3$ in Site 2 and 1.721g/$cm^3$ in Site 3) than in the control (1.721g/$cm^3$ in Site 1). Soil bulk density was decreased in the Rest-Year System areas of the national park. Amount of soil erosion was lower in the Rest-Year System areas ($0.017m^3$/km/yr in site 2, $0.023m^3$/km/yr in site 3) than in the control ($0.054m^3$/km/yr in site 1).

• 마이크로전자및패키징학회지
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• 제22권2호
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• pp.21-26
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• 2015

낮은 열전도도 및 높은 비표면적 특성으로 흡착제 및 가스센서 등 여러 응용 분야로 연구되고 있는 규칙적 메조기공 세라믹 소재는 폐기공 메조기공 구조와 개기공 메조기공 구조로 나뉜다. 이중 폐기공 메조기공 세라믹 소재는 개기공 메조기공 세라믹 소재보다 높은 기계적 특성을 가짐에도 내부에 존재하는 기공을 이용한 비표면적 증가에 한계가 있어 응용에 제약을 가지고 있다. 본 연구팀은 규칙적 폐기공 메조기공 타이타니아($TiO_2$)의 열처리 시간 변화에 따른 입자성장으로부터 폐기공 연결의 도입을 통하여 비표면적을 변화시키는 연구를 수행하고자 하였다. 열처리 시간 증가시 타이타니아 결정상의 변화는 없었으며 입자성장이 일어나게 되면서 기공구조의 무너짐 및 기공의 연결성 증가를 확인할 수 있었다. 24시간 열처리 시료의 경우, 기공률은 36.3%에 34.1%로 감소하였으나 기공의 연결도 증가로 인해 비표면적은 $48m^2/g$에서 $156m^2/g$으로 증가하였다. 이러한 비표면적의 증가는 CO 가스의 감응도 측정을 통하여 감응도가 약 7.4배 증가하는 것으로부터 확인될 수 있었다.

• 대한치과보철학회지
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• 제44권3호
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• pp.343-355
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• 2006

Statement of problem. The success of osseointegration can be enhanced with an implant that has improved surface characteristics. Anodic oxidation is one of the surface modifying method to achieve osseointegration. Voltage of anodic oxidation can change surface characteristics and cell activity Purpose. This study was performed to evaluate MG63 cell responses such as affinity, proliferation and to compare surface characteristics of anodic oxidized titanium in various voltage. Material and method. The disks for cell culture were fabricated from grade 3 commercially pure titanium,1 m in thickness and 12 mm in diameter. Surfaces of 4 different roughness were prepared. Group 1 had a machined surface, used as control. Group 2 was anodized under 220 V, group 3 was anodized under 300 V and group 4 was anodized under 320 V. The microtopography of specimens was observed by scanning electron microscope (JSM-840A, JEOL, Japan) and atomic force microscope(Autoprobe CP, Park Scientific Instrument, USA). The surface roughness was measured by confocal laser scanning microscope(Pascal, LSM5, Zeiss, Germany). The crystal structure of the titanium surface was analyzed with x-ray diffractometer(D8 advanced, Broker, Germany). MG63 osteoblast-like cells were cultured on these specimens. The cell morpholgy was observed by field emission electron microscope(Hitachi S-4700, Japan). The cell metabolic and proliferative activity was evaluated by MTT assay Results and conclusion. With in limitations of this in vitro study, the following conclusions were drawn. 1. In anodizing titanium surface, we could see pores which did not show in control group. In higher anodizing voltage, pore size was increased. 2. In anodizing titanium surface, we could see anatase. In higher anodizing voltage, thicker oxide layer increased crystallinity(anatase, anatase and rutile mixed). 3. MG63 cells showed more irregular, polarized and polygonal shape and developed more lamellipodi in anodizing group as voltage increased. 4. The activity of cells in MTT assay increased significantly in group 3 and 4 in comparison with group 1 and 2. However, there was no difference between group 3 and 4 at P<0.05. Proliferation of MG63 cells increased significantly in pore size($3-5.5{\mu}m$) of group 3 and 4 in comparison with in pore size($0.2-1{\mu}m$ ) of group 2.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1576-1578
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• 2004

The alumina membrane with nano sized pore was prepared from aluminum by anodic oxidation to apply for storage equipment, gas sensor and stamper. The pore size and cell size of the pores are controlled by anodic oxidation voltage. The alumina thickness was controlled by etching process using 0.2M $H_3PO_4$. The thickness of alumina on Si wafer was very accurately controlled by anodic oxidation time. Nickel with nano-sized grain was electroplated on the Au layer on silicon wafer. The fabricated pores on alumina membrane was the thickness of $7{\sim}10{\mu}m$ with straight nano-sized pore of 307${\sim}$120nm. The alumina by the etching process shows smooth surface. The size of Ni grain was 130nm and 250nm for 10mA/$cm^2$and 20mA/$cm^2$of electroplating currents, respectively.