• Korean Membrane Journal
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• 제8권1호
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• pp.67-73
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• 2006

Transparent materials are well known but preparation of transparent poly 2-hydroxyethyl methacrylate {poly (HEMA)} material by varying solvent is a new one and economically reliable. This material is prepared from hydroxyl based monomer HEMA by radical polymerization using benzoyl peroxide (BPO) as initiator and isobutanol, 2-butanol, 1-butanol, hexane and toluene as a solvent. The reaction temperature, time and stirring speed were set at $70^{\circ}C$, 4 hrs and 150 rpm, respectively. The polymer was characterized for functional group by IR spectroscopy. It was observed that the intensity of band at $1637 cm^{-1}$ a characteristic band of C=C stretching disappeared indicating that it was completely consumed after polymerization. It was observed that swelling percentage increases with increase as time passes but after a certain time a constant swelling percentage is achieved. SEM pictures reveals that poly (HEMA) prepared by different solvent shows pore with a distinguishable void up to several micrometers. The BET surface area, cumulative pore volume and average pore diameter is greater in poly (HEMA) prepared by hexane as a solvent compared to other solvents. Poly (HEMA) prepared by 1-butanol as a solvent shows higher glass transition temperature compared to other solvents. Poly (HEMA) prepared by different solvents shows $90{\sim}94%$ light transmission property from light transmission measurement and looks transparent.

• 한국표면공학회지
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• 제47권3호
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• pp.121-127
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• 2014

In this study, in order to improve corrosion resistance and wear resistance of aluminum, surface treatment was made by anodizing with oxalic acid solution and sealing with nano-diamond powder. Average size of nano-diamond powder was 30nm. Anodizing with oxalic acid made many pores in the aluminum oxide layer. Pore size and oxide thickness were investigated by scanning electron microscope (SEM). Pore size increased as temperature increased and voltage increased. It was possible to make oxide layer with pore diameter more than 50 nm. Oxide thickness increased as temperature and voltage and treatment time increased. Oxide layer with above $10{\mu}m$ thickness was made. Aluminum oxide layer with many pores was sealed by water with nano-diamond powder. Surface morphology was investigated by SEM. After sealing treatment with nano-diamond powder, corrosion resistance, wear resistance and hardness increased.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.851-856
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• 2011

본 연구에서는 하수슬러지의 열분해로 촤를 제조하였고, 열분해 반응 조건이 슬러지 촤의 특성에 미치는 영향을 조사하였다. 열분해 온도가 $300^{\circ}C$에서 $800^{\circ}C$로 증가함에 따라 슬러지 char의 비표면적은 증가하였으나, $700^{\circ}C$에서는 일시적으로 감소하였다. 열분해 속도는 char의 비표면적과 기공부피에 미치는 영향이 크지 않은 것으로 나타났다. 반면, 열분해 반응시간이 증가함에 따라 비표면적과 기공부피는 증가하였으나, 평균 기공크기는 감소하는 결과를 나타내었다.

• 공업화학
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• 제28권6호
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• pp.649-654
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• 2017

제주도에서 다량 발생하고 있는 폐감귤박을 활성화제로 KOH를 사용하여 활성탄을 제조하였고, 제조된 활성탄의 특성을 검토하였다. KOH 침적비율(100~300%), 활성화 온도($400{\sim}900^{\circ}C$) 및 활성화 시간(0.5~1.5 h)의 조건에서 각 조건이 증가할수록 요오드 흡착능은 증가하였으나 활성탄의 수율은 감소하였다. 그리고 활성화 시간의 경우 1.5 h 이상에서는 요오드 흡착능 및 활성탄 수율에서 비슷하였다. 또한 KOH 침적비율이 증가할수록 비표면적 및 세공부피는 증가하였으나 세공크기는 감소하였으며, 제조된 평균 세공크기는 $20{\sim}25{\AA}$이었다. KOH의 침적비율 300%, 활성화 온도 $900^{\circ}C$, 활성화 시간 1.5 h에서 제조된 활성탄은 비표면적 및 요오드 흡착능이 각각 $1,527m^2/g$ 및 1,246 mg/g으로 가장 높았다.

• 한국분말재료학회지
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• 제22권3호
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• pp.216-220
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• 2015

Vertically oriented nickel nanowire arrays with a different diameter and length are synthesized in porous anodic aluminium oxide templates by an electrodeposition method. The pore diameters of the templates are adjusted by controlling the anodization conditions and then they are utilized as templates to grow nickel nanowire arrays. The nickel nanowires have the average diameters of approximately 25 and 260 nm and the crystal structure, morphology and microstructure of the nanowires are systematically investigated using XRD, FE-SEM and TEM analysis. The nickel nanowire arrays show a magnetic anisotropy with the easy axis parallel to the nanowires and the coercivity and remanence enhance with decreasing a wire diameter and increasing a wire length.

• 펄프종이기술
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• 제42권1호
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• pp.7-12
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• 2010

Morphological characteristics of hemp fiber were investigated using a light microscope in order to provide fundamental data for the use of hemp as a papermaking law material. Phloem of hemp is composed of cortical parenchyma cells and bast fiber with thick walls while xylem is composed of vessel, wood fiber and ray parenchyma cells. Also there are solitary pore and radial pore multiple which exist in diffuse porous pattern. Ray cells consist of uniseriate rays and thin walled ray parenchyma cells. Wood fibers are composed of three types: a large diameter fiber with longer length; a large diameter fiber with shorter length; a small diameter fiber with medium length. Vessel elements are composed of: a medium length one; a longer length one; the one whose both end walls have ligules or tails. Parenchyma cells in xylem and pit parenchyma cells have completely different size and shape. For bast fiber, the average length is about 4.4 mm and the width is about $30.5\;{\mu}m$; for vessel element, $600.0\;{\mu}m$ in length and $493.6\;{\mu}m$ in width; for wood fiber, $1000\;{\mu}m$ and $38.9\;{\mu}m$; for parenchyma cell, $50\;{\mu}m$ and $26.4\;{\mu}m$.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.478-481
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• 1997

A technique or the preparation of porous polyurethane vascular prostheses was investigated. Small-diameter vessels are not in general clinical use due to their limited long-term biocompatibility and low patency rates in experimental trial. These limits are mainly due to the failure of mechanical unction of the vascular grafts. This failure has been suggested to result partially from compliance mismatch. The long-term patency is considered to depend critically on the properties of the material and the fabrication process of the graft. So the control of pores is very important and main points to develop a available vascular grafts. Two-kind polymer sheets was compared. One was the porous PU-sheet made at room temperature by the solvent/non-solvent exchange. And the other was the porous PU-sheet which was fabricated by thermal phase transition and solvent-/non-solvent exchange using the thermal controller. The polymer sheets had a uniform pore size and pore occupation. According to the result of the above experiments, polyurethane solution was injected into a mold designed or U-type tube. The average pore size and pore occupation were easily changed by changing polyurethane concentration, freezing temperature, and methods. This technique can give a proper pore size ($10{\sim}45\;{\mu}m$) or tissue in growth, and suitable compliances or matching with arteries and veins. Besides, the fabrication of more complicated shaped vessels such as the U-type vascular grafts is easily controlled by using the fixed mold. this method might give a desired compliant graft or artificial implantation with the presently valid medical polymers.

• 한국재료학회지
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• 제23권1호
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• pp.24-30
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• 2013

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 ($700^{\circ}C$ to $850^{\circ}C$). 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 $800^{\circ}C$ 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.

• 대한토목학회논문집
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• 제26권5A호
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• pp.927-934
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• 2006

콘크리트 구조물의 고성능화가 요구됨에 따라 고성능 콘크리트에 관한 연구가 활발히 진행되어 왔으며, 특히 고강도 콘크리트에 관한 많은 연구가 이루어지고 있다. 고강도 콘크리트를 제조하기 위해서는 혼화재료의 첨가가 필수적이라 할 수 있으며, 지금까지는 실리카 퓸을 주로 사용하여 왔으나, 최근에는 실리카 퓸과 대등한 성능을 가지면서 실리카 퓸보다 저가인 메타카올린을 사용한 고강도 콘크리트에 관한 연구가 많이 진행되고 있다. 본 연구에서는 메타카올린을 사용한 고강도 콘크리트의 특성을 규명하기 위하여 시멘트 페이스트 시험체의 XRD 및 SEM 분석을 통하여 메타카올린의 포졸란 반응을 고찰하였고, 콘크리트 시험체를 제작하여 수은압입법으로 공극구조를 분석하여 압축강도와의 상관성을 도출하였다. 그 결과, 메타카올린의 대체율이 증가할수록 평균 공극직경은 작아지고 압축강도는 증가하는 것으로 나타났으며, 본 연구에서는 $10nm{\sim}10{\mu}m$의 모세관 공극량과 압축강도와의 회귀분석 결과 이들 사이의 결정계수는 약 0.93 정도의 높은 상관성이 있었고, 메타카올린의 적정 대체율은 10~15%로 판단된다.

• 한국막학회:학술대회논문집
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• 한국막학회 1992년도 추계 총회 및 학술발표회
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• pp.53-54
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• 1992

In this study characteristics of dynamic filters utilizing Taylor vortices were investigated both experimentally and theoretically. With fine silica slurry of 4.0 $\mu$m in average size experiments were conducted in Taylor vortices generated between the rotating inner cylinder consisting of microfiltration membrane of 1.2 $\mu$m in average pore size and the stationary outer cylinder. The diameter of the inner cylinder was 5.2 cm. Four outer cylinders having different diameters were manufactured and therefore four types of dynamic filters having the different ratio of the annular gap to the inner cylinder radius, i.e. 0.17, 0.33, 0.54, 0.65, were used as the experimental apparatus, as shown in Fig. 1.