• Composites Research
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• v.17 no.3
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• pp.1-7
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• 2004

In the vacuum assisted RTM (VARTM) process that has become the center of attention for manufacturing massive composite structures, a good evacuation of air in the fiber preform is recognized as the prime factor. The microvoids, or the dry spots, are formed as a result of improper gate/vent locations and the mold geometry. The non-uniform resin velocity at the flow front leads to the formation of microvoids in the fibers, whereas the air in the microvoids can migrate along with the resin flow during mold filling. The residual air in the internal voids of a composite structure may cause a degradation of the mechanical properties as well as the structural failure. In this study, a unified macro- and micro analysis methods were developed to investigate the formation and transport of air in resin during VARTM process. A numerical simulation program was developed to analyze the three-dimensional flow pattern as well as the macro- and microscopic distribution of air in a composite part fabricated by VARTM process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.156-157
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• 2014

수소 분리막은 수소 분리층과 지지체로 구분되며, 수소 분리막의 수소 투과 및 선택도는 지지체의 표면조도, 평탄도 및 거대기공 크기에 크게 의존한다. 본 연구에서는 표면연마 및 $ZrO_2$ 파우더 매립을 사용한 표면처리 공정을 통해 다 공성 스테인레스 강 지지체의 표면조도 및 평탄도와 거대기공을 제어함으로써 균일하고 치밀한 분리층을 형성 할 수 있었으며, 상용화 공정($350^{\circ}C{\sim}500^{\circ}C$, 1bar(${\Delta}P$))에서 무한대의 수소 선택도와 $17.5ml/min{\cdot}cm^2{\cdot}atm$의 수소 투과도를 얻을 수 있었다.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.524-535
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• 2018

In this study, macroporous titania powders were synthesized utilizing the emulsion-assisted self-assembly to apply the removal of B. subtilis under UV irradiation, and the results were compared with the bactericidal effect of commercial titania nanoparticles. By changing the pore size of the porous titania powder, the reduction of B. subtilis by photocatalytic effect was measured, and the bactericidal capacity of the porous particles according to the pore size was compared in order to derive the optimum condition of the sterilization experiment. It was observed that the sterilization effect increased as the pore size became smaller, and it was confirmed that more than 50% of B. subtilis cold be removed for 1 hour of UV irradiation. Also, in order to promote the generation of active chemical species, a diluted solution of hydrogen peroxide was combined with the photocatalytic sterilization method, resulting in the removal of most of the strain after ultraviolet irradiation for 1 hour.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.58-65
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• 2016

This study was a preparatory experiment aimed the development of membrane scaffolds for tissue engineering. A PCL composite solution contained sodium chloride(NaCl). PCL porous membrane scaffolds were formed on a glass casting plate using a film applicator and immersed in distilled water to remove the NaCl reaching after drying. NaCl was used as a pore former for a 3 dimensional pore net-work. The dry condition parameters were $4^{\circ}C$, room temperature (RT) and $40^{\circ}C$ for each different temperatures in the drying experiment. SEM revealed the morphology of the pores in the membrane after drying and evaluated the in vitro cytotoxicity for basic bio-compatibility. The macro and micro pores existed together in the scaffold and showed a 3-dimensional pore net-working morphology at RT. The in vitro cytotoxicity test result was "grade 2" in accordance with the criterion for cytotoxicity by ISO 10993-5. The dry condition affected the formation of a 3 dimensional pore network and micro and macro pores. Therefore, these results are expected provide the basic process for the development of porous membrane scaffolds to control degradation and allow drug delivery.

• Membrane Journal
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• v.26 no.1
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• pp.26-31
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• 2016

Polycaprolactone (PCL) has been fabricated into the membrane type scaffolds of 3 dimensional pore network for the tissue engineering applications by the blade method of salt (NaCl) leaching and solution casting. In this study, the experimental designs have each conditions of drying temperature, salt particle size, salt content. The modified dispensing pump connected up to homogenizing mixer system is used for mixing the $PCL/CHCl_3$ solution and NaCl particles. The membrane fabricated use by the film applicator to poured mixed solution on the glass plate. The great pore by NaCl particles and the small pore by the evaporated $CHCl_3$ in the frame wall of great pores are multiply formed in membrane scaffolds.

• 기계와재료
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• v.22 no.4
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• pp.36-48
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• 2010

고분자의 자기조립화 구조를 주형 (template)으로 이용하여 합성되는 메조다공성 물질은 고분자 주형 제거 후 나노크기의 규칙 기공구조가 이루어내는 거대한 비표면적을 제공한다. 이 거대 비표면적을 이루는 나노기공은 광학, 에너지, 환경 및 생체 등 여러 가지 소재분야에서 높은 활용가능성을 가진다. 종래의 연구는 메조다공성 물질의 다양한 응용가능성을 제안하기 위한 재료합성 및 설계에 초점이 맞추어져 있었으나 최근에는 기능부여를 통한 실질적 활용법 제안으로 그 패러다임이 전환되고 있다. 특히, 메조다공성 물질의 에너지 저장 및 발현소재로서의 가능성과 생체활성물질 전달 및 생체골 형성능이 확인되면서 에너지와 바이오 분야에서 특히 높은 관심이 주목되고 있다. 본고에서는 이 중 생체소재로서의 메조다공성 물질 설계 및 응용과 관련된 연구 현황을 정리하였다.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.296-303
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• 2021

The objective of this study is to investigate the applicability of a Cu-supported honeycomb catalyst as a catalyst for decomposition of a low toxic liquid propellant based on ammonium dinitramide (ADN). A mixture of copper, lanthanum, and alumina was supported on the honeycomb support by wash coating to prepare a Cu-La-Al/honeycomb catalyst. We elucidated that the effect of metal loading on the physicochemical properties of Cu-La-Al/honeycomb catalyst and catalytic performance in decomposition of the ADN-based liquid propellant. As the number of wash coatings increased, the amount of active metal Cu was increased to 4.1 wt%. The BET surface area of the Cu-La-Al/honeycomb catalyst was in the range of 3.1~4.1 ㎡/g. The micropores were hardly present in Cu-La-Al/honeycomb catalysts, however, the mesopores and macropores were well developed. The Cu (2.7 wt%)-La-Al/honeycomb catalyst exhibited the highest activity in the decomposition of the ADN-based liquid propellant, which is attributed to the largest surface area, the largest pore volume, and the well-developed mesopores and macropores.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.677-682
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• 2003

The physical properties of sintered body made from 3 kinds of slip, F (Flocculated), M (Moderate), and D (Dispersed) for coal fly ash 70-clay 30 (wt%) were studied in terms of slip states and pore size distribution of sintered bodies. The floc particle size distribution for slip F was wider than slip D and the slip F contained flocs larger than 11 $\mu\textrm{m}$. The pore size distribution of the green body of all slips ranged over 1∼4 $\mu\textrm{m}$. The pores smaller than 1 $\mu\textrm{m}$ almost disappeared during the sintering process, while the larger pore of 2.5∼3 $\mu\textrm{m}$ growed by 1 $\mu\textrm{m}$. The pore distribution for the green body of slip F became a narrow in width and high in height after sintering and the large pore limit in a slip F sintered body was 5.1 $\mu\textrm{m}$ which is smaller than that of other slip. The slip F rather flocculated was favorable over slip D well dispersed, in offering a higher compressive strength. From these results, the mechanical strength of sintered body is dependent on the pore distribution which could be controlled by dispersion state of the slips.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1097-1104
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• 1997

인산형 연료전지(PAFC)용 전해질 매트릭스의 표면 거칠기를 감소시켜 분극저항을 줄이고 작업성을 향상시키기 위해 SiC whisker를 사용하여 일반적인 테이프 캐스팅법으로 제조된 매트릭스의 거친 표면을 평탄화 처리하였다. 구형 입자의 분무공정을 이용하여 표면 평탄화 처리(process l)하는 경우와 롤링을 이용하여 표면 평탄화 처리(process 2)하는 두가지 공정을시도하였으며, 두가지 공정 모두 기공율과 인산 함침도를 유지시키면서, 매트릭스의 표면 거칠기를 감소시키고 기공압, 가소성 및 인장강도를 향상시킬 수 있었다. 위와 같이 제조한 매트릭스로 연료전지를 구성하여 교류 임피던스 분석을 한 결과, 표면 평탄화 처리는 매트릭스 표면의 거칠기를 감소시킴으로써 전극과의 접촉시 계면에서의 분극 저항을 감소시켜 전지성능을 향상시키는 것으로 나타났다. process 2는 표면의 거칠기 감소뿐 아니라 표면에서의 인산함침도가 커서 가장 우수한 전지특성을 나타내었으며, process 1은 매트릭스 표면에 불규칙하게 존재하는 거대 기공을 완전히 제거하고 기공압을 크게 향상시킬 수 있기 때문에 대형의 매트릭스 제조를 가능하게 하였다.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.229-234
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• 2004

In this study, we proposed new forming process for a porous ceramic body with unique pore structure. h tubular-type porous NiO-YSZ body with radially aligned pore channels was prepared by freeze-drying of aqueous slurry. A NiO-YSZ slurry was poured into the mold, which was designed to control the crystallization direction of the ice, followed by freezing. Thereafter the ice was sublimated at a reduced pressure. SEM observations revealed that the NiO-YSZ porous body showed aligned large pore channels parallel to the ice growth direction, and fine pores are formed around the outer surface of the tube. It was considered that the difference in the ice growth rate during the freezing process resulted in such a characteristic microstructure. Bilayer consisting of dense thin electrolyte film of YSZ onto the tubular type porous body has been successfully fabricated using a slurry-coating process followed by co-firing. It was regarded that the obtained bilayer structure is suitable for constructing electrode-support type electrochemical devices such as solid oxide fuel cells.