• 세라미스트
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• 제22권3호
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• pp.243-255
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• 2019

Graphene, a two-dimensional material with a single atomic layer, has recently become a major research focus in various applications such as electronic devices, sensors, energy storage, catalysts, and adsorbents, because of its large theoretical surface area, excellent electrical conductivity, outstanding chemical stability, and good mechanical properties. Recently, 3D nanoporous graphene structures have received tremendous attention to expand the application of 2D graphene. Here, we overview the synthesis of 3D nanoporous graphene network structure with two-dimensional graphite oxide sheets, the control of porous parameters such as specific surface area, pore volume and pore size etc, and the modification of electronic structure by heteroatom doping along with its various applications. The 3D nanoporous graphene shows superior performance in diverse applications as a promising key material. Consequently, 3D nanoporous graphene can lead the future for advanced nanotechnology.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.629-632
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• 1999

For replacing Li metal ai Lithium ton Bakery(LIB) system. we used carbon powder material which prepared by pyrolysis of phenol resin as starting material. It became amorphous carbon by pyrolysis through it\`s self condensation by thermal treatment. Amorphous carbon can be doped with Li intercalation and deintercalation because it has wide interlayer. however it has a problem with structural destroy causing weak carbon-carbon bond. So. we used ZnCl$_2$ as the pore-forming agent. This inorganic salt used together with the resin serves not only as the pore-forming agent to form open pores, which grow Into a three-dimensional network structure in the cured material, foul also as the microstructure-controlling agent to form a loose structure dope with bulky dopants. We analyzed SEM in order to find to different of structure. and can calculate distance of interlayer. CV test showed oxidation and reduction

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2009년도 학술대회 초록집
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• pp.147-154
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• 2009

암석의 속도를 정확히 예측하기 위해서는 속도에 1차적인 영향을 미치는 공극구조의 연구가 필수적이다. 이에 본 연구에서는 고해상도 구조 해석에 가장 많이 사용하고 있는 X선 토모그래피 방법을 이용하여 공극구조를 획득하였다. 그러나 X선 토모그래피 방법의 경우 그 역산과정에서 발생하는 smoothing 효과에 의해 공극구조가 왜곡될 수 있다.이를 간단한 공극구조 생성 방법인 single threshold 방법으로 이분화 할 경우 grain contact 부분이 명확히 표현되지 않아 입자의 접촉면적에 좌우되는 속도의 경우 많은 오차를 야기한다. 또한 grain contact의 정확한 기술을 위해서는 고해상도 토모그램 획득이 매우 중요하며, 해상도에 따른 속도의 변화양상 또한 정량적 분석이 필요한 부분이다. 이를 위해 본 연구에서는 영상처리 기법을 적용하여 다양한 이분화를 시도하고, 서로 다른 해상도의 토모그램을 이용하여 이들이 속도 계산에 미치는 영향을 분석하였다. 다양한 영상처리 기법을 적용한 결과 single threshold 방법으로 이분화 한 결과보다 정확한 접촉면적을 보여주는 이분화 결과를 얻을 수 있었지만 실제 계산된 속도에서는 그 향상 정도가 미미하였다. 고해상도 토모그램을 이용한 경우에는 입자의 grain contact이 명확하게 표현되었고, 속도 또한 상당히 향상된 결과를 보여주었다. 결론적으로 디지털 공극구조에서 시뮬레이션을 통한 속도 예측의 경우, 입자의 접촉 부분을 정확히 기술 할 수 있는 높은 해상도의 토모그램이 필수적이며, smoothing 효과의 제거 등의 영상처리와 병행된다면 보다 정확한 암석의 속도 예측이 가능할 것으로 판단된다.

• 한국재료학회지
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• 제18권3호
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• pp.163-168
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• 2008

The morphology of three-dimensional (3D) cross-linked electrodeposits of copper and tin was investigated as a function of the content of metal sulfate and acetic acid in a deposition bath. The composition of copper sulfate had little effect on the overall copper network structure, whereas that of tin sulfate produced significant differences in the tin network structure. The effect of the metal sulfate content on the copper and tin network is discussed in terms of whether or not hydrogen evolution occurs on electrodeposits. In addition, the hydrophobic additive, i.e., acetic acid, which suppresses the coalescence of evolved hydrogen bubbles and thereby makes the pore size controllable, proved to be detrimental to the formation of a well-defined network structure. This led to a non-uniform or discontinuous copper network. This implies that acetic acid critically retards the electrodeposition of copper.

• 멤브레인
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• 제26권1호
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• pp.26-31
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• 2016

폴리카프로락톤(PCL)에 NaCl을 혼합한 용액을 블레이드법에 의하여 막형태로 제조한 후 NaCl을 추출하는 염출법을 이용하여 조직공학적으로 사용할 3차원 다공망을 갖는 멤브레인 형태의 지지체를 제조하였다. 본 연구에서는 성형된 멤브레인의 건조조건과, NaCl 입자의 크기, NaCl의 혼합량을 각각 다르게 하여 제조하였다. 별도로 제작한 고분자용액 공급장치를 이용하여 PCL/클로로포름($CHCl_3$) 용액에 NaCl 입자가 균일하게 혼합된 용액을 유리판에 분주하여 필름 어플리케이터를 사용하여 블레이드법에 의한 멤브레인을 제조하였다. 멤브레인 지지체에는 NaCl 입자에 의한 거대기공과 거대기공을 이루는 구조벽에서는 $CHCl_3$의 증발에 의한 미세기공이 함께 복합적으로 상호 연결되어 형성되었다.

• Computers and Concrete
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• 제7권1호
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• pp.39-51
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• 2010

The system of pores of autoclaved aerated concrete (AAC) is described by the so-called cherry-pit model, a random system of partially interpenetrating spheres. For the simulation of fracture processes, the solid phase is approximated by an irregular spatial network of beams obtained by means of the so-called radical tessellation with respect to the pore spheres. FE calculations using standard software (ANSYS) yield the strain energies of the beams. These energies are used as fracture criterion according to which highly loaded beams are considered as broken and are removed from the network. The paper investigates the relationship between mean fracture strength and microstructure for structures close to real AAC samples and virtual structures with particular geometrical properties.

• 멤브레인
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• 제28권3호
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• pp.214-219
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• 2018

본 연구에서는 비용매 유도 상분리와 소결 공정을 혼용하여 기체 및 액체에 대하여 슈퍼플럭스 거동을 보이는 니켈 모세관 지지체를 성공적으로 제조하였다. 니켈 모세관 전구체는 니켈, 폴리술폰, DMAC, PEG를 이용하여 도프용액을 제조한 후 NIPS 공정에 의하여 제조된 후에, 다양한 소결온도에서 수소 분위기 조건에서 소결하여 니켈 모세관 지지체를 제조하였다. 최적의 니켈 모세관 지지체는 $950^{\circ}C$ 소결온도에서 얻어졌는데 외경 $722{\mu}m$, 내경 $550{\mu}m$, 두께 $94{\mu}m$이었다. 니켈 모세관 지지체 기공율은 26%, 평균 기공경은 $4{\mu}m$이었으며 3차원으로 서로 연결된 기공구조를 갖고 있었다. 그리고 파괴하중은 2.84 kgf, 파괴 연신율은 13%이었다. 니켈 모세관 지지체의 He, $N_2$, $O_2$, $CO_2$에 대한 단일 기체 투과도는 상온에서 각각 432,327, 281,119, 264,259, 193,143 GPU로 슈퍼플럭스 거동을 보였다. 이는 3차원적으로 서로 연결된 $4{\mu}m$ 크기 마크로기공을 통하여 viscous flow가 일어났기 때문에 나타나는 현상으로 설명되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.363-363
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• 2010

The high capillarity of a plastic fiber network having superhydrophilic Si-DLC coating is studied. Although the superhydrophilic surface maximize wetting ability on the flat surface, there remains a requirement for the more wettable surface for various applications such as air-filters or liquid-filters. In this research, the PET non-woven fabric surface was realized by superhydrophilic coating. PTE non-woven fabric network was chosen due to its micro-pore structure, cheap price, and productivity. Superhydrophobic fiber network was prepared with a coating of oxgyen plasma treated Si-DLC films using plasma-enhanced chemical vapor deposition (PECVD). We first fabricated superhydrophilic fabric structure by using a polyethylene terephthalate (PET) non-woven fabric (NWF) coated with a nanostructured films of the Si-incorporated diamond-like carbon (Si-DLC) followed by the plasma dry etching with oxygen. The Si-DLC with oxygen plasma etching becomes a superhydrophilic and the Si-DLC coating have several advantages of easy coating procedure at room temperature, strong mechanical performance, and long-lasting property in superhydrophilicity. It was found that the superhydrophobic fiber network shows better wicking ability through micro-pores and enables water to have much faster spreading speed than merely superhydrophilic surface. Here, capillarity on superhydrophilic fabric structure is investigated from the spreading pattern of water flowing on the vertical surface in a gravitational field. As water flows on vertical flat solid surface always fall down in gravitational direction (i.e. gravity dominant flow), while water flows on vertical superhydrophilic fabric surface showed the capillary dominant spreading.

• 약학회지
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• 제30권6호
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• pp.306-310
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• 1986

The release of heparin from monolithic devices composed of different ratios of polyethylene oxide(PEO MW 20,000) and polydimethylsiloxane was investigated. Water soluble PEO plended into the polydimethylsiloxane proved a controlled release of heparin. The release rate of heparin could be controlled by varying the content of PEO and loading dose of heparin. The release rate of heparin from the devices increased as the content of PEO and heparin in the devices increased. The release rate of heparin from devices were related to nature of solute(ionic strength) and temperature. The release mechanism may be associated with the creation of pore or domine through the devices the water-uptake and the change in the physical structure of the polydimethysiloxane network.

• 한국세라믹학회지
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• 제44권3호
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• pp.162-168
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• 2007

Silica wet gels were prepared ken water glass ($29\;wt%\;SiO_{2}$) by using Amberlite as a ion exchange resin. After washing in distilled water, the wet gels were further aged in a solution of TEOS/EtOH to strengthen of 3-dimensional network structure. As increase TEOS content in aging solution, BET surface area and porosity of the ambient dried silica aerogels were significantly decreased, and average pore diameter was also decreased 30 nm to -10 nm. Also, higher density and compressive strength were obtained in case of higher TEOS content. This is due to precipitation of $SiO_{2}$ nano particles by TEOS. Hence, TEOS addition plays an important role of both strengthening and stiffness of silica wet gel network. By adding over 30 vol% TEOS, a crack-free monolithic silica aerogel tiles were obtained and its density, compressive strength, and thermal conductivity were shown $0.232g/cm^{3}$, 7.3 MPa, and 0.029 W/mk, respectivly.