• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.438-439
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• 2006

Pure and stable YAG $(Y_3Al_5O_{12})$ powders were synthesized by a PVA (polyvinyl alcohol) polymer solution technique. PVA was used as an organic carrier for the precursor ceramic gel. The precursor gels were crystallized to YAG at relatively a low temperature of $900\;^{\circ}C$. The synthesized powders, which have nano-sized primary particles, were soft and porous, and the porous powders were ground to sub-micron size by a simple ball milling process. The ball-milled powders were densified to 94% relative density at $1500\;^{\circ}C$ for 1h. In this study, the characteristics of the synthesized YAG powders were examined.

• 전기화학회지
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• 제10권4호
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• pp.295-300
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• 2007

A new characterization method using a porous plug model was proposed to determine the degree of sulfonation (DS) of ionomer binder with respect to the membrane used in membrane-electrode assemblies (MEAs) and to analyze the fraction of proton pathways through ionomer-catalyst combined electrodes in MEAs for polymer electrolyte fuel cells (PEFCs). Sulfonated poly(ether ether ketone) was prepared to use a polymeric electrolyte and laboratory-made SPEEK solution (5wt.%, DMAc based) was added to catalyst slurry to form catalyst layers. In case of the SPEEK-based MEAs in this study, DS of ionomer binder for catalyst layers should be the same or higher than that of the SPEEK membrane used in the MEAs. The porous plug model suggested that most of protons were via the ionomer binder (${\sim}92.5%$) bridging the catalyst surface to the polymeric electrolyte, compared with the pathways through the alternative between the interstitial water on the surface of ionomer binder or catalyst and the ionomer binder (${\sim}7.3%$) and through only the interstitial water on the surface of ionomer or catalyst (${\sim}0.2%$) in the electrode of the MEA comprising of the sulfonated poly(ether ether ketone) membrane and the 5wt.% SPEEK ionomer binder. As a result, it was believed that the majority of proton at both electrodeds moves through ionomer binder until reaching to electrolyte membrane. The porous plug model of the electrodes of MEAs reemphasized the importance of well-optimized structure of ionomer binder and catalyst for fuel cells.

• 한국세라믹학회지
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• 제51권6호
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• pp.539-543
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• 2014

Foam type porous silicon carbide ceramics were fabricated by a polymer replica method using polyurethane foam, carbon black, phenol resin, and silicon powder as raw materials. The influence of the C/Si mole ratio of the ceramic slurry and heat treatment temperature on the porous silicon carbide microstructure was investigated. To characterize the microstructure of porous silicon carbide ceramics, BET, bulk density, X-ray Powder Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were employed. The results revealed that the surface area of the porous silicon carbide ceramics decreases with increased heat treatment temperature and carbon content at the $2^{nd}$ heat treatment stage. The addition of carbon to the ceramic slurry, which was composed of phenol resin and silicon powder, enhanced the direct carbonization reaction of silicon. This is ascribed to a consequent decrease of the wetting angles of carbon to silicon with increasing heat treatment temperature.

• 한국재료학회지
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• 제16권11호
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• pp.715-718
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• 2006

Porous hydroxyapatite (HAp) scaffolds have been prepared by using the slurry including HAp and magnesia based on the replication of polymer sponge substrate. The influence of MgO content in slurry on the pore morphology and size, density, porosity, and mechanical strength of porous HAp scaffolds was investigated. The obtained scaffolds with average pore sizes ranging 150 to 300 mm had open, relatively uniform, and interconnected porous structure regardless of MgO content. As the MgO content increased, the pore network frame of scaffolds became to be relatively stronger, even though the pore size was not much changed. The compressive strength of the scaffolds increased rapidly with the increase of MgO content because of increasing the pore wall thickness and density of the scaffolds. As a result, the porosity, density, and compressive strength of the porous HAp scaffolds prepared by the sponge method were significantly affected by the addition of MgO.

• 폴리머
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• 제32권4호
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• pp.328-333
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• 2008

삼투압을 이용한 약물전달시스템은 소화관내의 물이 다공성막을 통하여 시스템 내부로 침투하면 시스템 내부에 있던 삼투압물질과 섞여 삼투압을 발생시키고, 이 삼투압의 힘으로 시스템 내부에 있는 약물을 시스템 외부로 일정한 속도로 방출하는 제제기술이다. 이러한 삼투압을 이용하여 상용화된 대표적인 제품으로 니페디핀을 모델약물로 한 타블렛제형인 Procadia $XL^{(R)}$(Pfizer)과 $Adalat^{(R)}$(Bayer)가 널리 상용화되어 있다. 이번 연구에서는 타블렛 형태의 삼투압정을 유동층코팅 기술을 이용하여 삼투성펠렛으로 제조하였다. 삼투성펠렛은 수팽윤성 고분자와 삼투염을 포함한 시드층, 모델약물인 니페디핀을 포함하는 약물층 그리고 약물의 방출을 조절할 수 있는 다공성막으로 구성되어 있다. 본 연구에서는 다공성막으로 사용되는 초산셀룰로오스(CA)와 $Eudragit^{(R)}$ RS의 구성비와 코팅두께에 따른 약물방출 거동을 확인하였으며, 다공성막의 구성물질인 CA의 비가 증가할수록 또한 다공성막의 코팅두께가 증가할수록 같은 측정시간 때에 약물의 방출이 낮게 나타남을 확인하였다. 약물방출 전후의 펠렛의 형태를 확인하기 위하여 SEM을 측정하였다.

• 한국세라믹학회지
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• 제48권5호
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• pp.412-417
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• 2011

Formation and characterization of hydroxyapatite-based porous ceramics derived from polymer pyroysis were investigated. Polymer based process is chosen for preparing porous hydroxyapatite-based ceramics having a high mechanical strength. The hydroxyapatite-based porous ceramic was prepared by a self-blowing process of a polymethylsiloxane with filler and pyrolyzed at above $1000^{\circ}C$. Biphasic material consisted of hydroxyapatite and CaO has been prepared by solid state reaction from calcium hydroxide($Ca(OH)_2$) and calcium hydrogen phosphate dihydrate($CaHPO_4{\cdot}2H_2O$) as a filler material. The influence of filler content on mechanical properties was evaluated. The change of crystalline phase, microstructure and mechanical properties were investigated and discussed.

• 폴리머
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• 제38권3호
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• pp.293-298
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• 2014

본 연구에서는 방사선을 이용하여 다공성 polytetrafluoroethylene(PTFE) 지지체에 acrylonitrile(AN)과 친수성 작용기를 가진 sodium allylsulfonate(SAS)를 접목시켜 복합 연료전지막의 지지체로 사용되는 친수화 다공성 지지체를 제조하였다. SAS/AN의 몰비율, 단량체 농도, 방사선의 조사선량에 변화를 주어 제조된 지지체의 물성을 평가하였다. 제조된 지지체의 FTIR 분석을 통하여 각 단량체들이 다공성 PTFE 지지체에 성공적으로 그래프팅되었음을 확인하였다. 또한 FE-SEM과 gurley number 측정을 이용하여 그래프트율이 증가할수록 지지체 표면의 기공이 감소하는 것을 관찰하였고, 그래프트율, 접촉각, TBO(toluidine blue O) uptake 분석을 통해 그래프트율이 증가됨에 따라 제조된 지지체의 친수화도가 증가하는 것을 확인하였다.

• Macromolecular Research
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• 제13권1호
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• pp.73-79
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• 2005

Poly(L-lactic acid-co-succinic acid-co-l,4-butane diol) (PLASB) was synthesized by direct condensation copolymerization of L-lactic acid (LA), succinic acid (SA), and 1,4-butanediol (BD) in the bulk using titanium(IV) butoxide as a catalyst. The weight-average molecular weight ofPLASB was $2.1{\times}10^{5}$ when the contents of SA and BD were each 0.5 mol/100 mol of LA. Electrospinning was used to fabricate porous membranes from this newly synthesized bioabsorbable PLASB dissolved in mixed solvents of methylene chloride and dimethylformamide. Scanning electron microscopy (SEM) images indicated that the fiber diameters and nanostructured morphologies of the electrospun membranes depended on the processing parameters, such as the solvent ratioand the polymer concentration. By adjusting both the solvent mixture ratio and the polymer concentration, we could fabricate uniform nanofiber non-woven membranes. Cell proliferation on the electrospun porous PLASB membranes was evaluated using mouse fibroblast cells; we compare these results with those of the cell responses on bulk PLASB films.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.631-632
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• 2013

• Journal of Forest and Environmental Science
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• 제14권1호
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• pp.1-13
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• 1998

주요 침 활엽수재에 대하여 methyl methacrylate를 이용하여 만든 목재-polymer복합체에 대하여 polymer의 분포와 존재상태등을 목재의 조직학적인 면에서 조사하였으며 그것을 요약하면 다음과 같다. 1. polymer의 침투성은 수종에 따라 다르며 수종고유의 특성에 따라 다르다. 낙엽송은 침투성이 대단히 나쁘며 활엽수재에 있어서는 환공재가 산공재보다 침투성이 양호 하였다. 2. 횡단면에서 침투성이 가장 양호하며 방사단면과 접선단면에서의 주입은 저하되고 양자의 차이는 거의 없었다. 3. 동일 수종에서는 변재가 섬재보다 침투성이 양호 하였다. 수종에 따라 변심재간에 침투성이 다른 것은 심재화에 의한 tyloses의 형성 또는 도관중의 침착물에 의한 것으로 생각되고 있다. 4. 환공성 수종에서는 조재부가 만재부보다 polymer의 침투성이 양호 하였으며 산공재에서는 반대로 만재부가 조재부보다 침투성이 양호하였다. 5. 도관의 크기와 침투성과의 사이에는 명확한 상관이 없는 것으로 생각된다. 도관의 직경이외에도 도관의 비율, tyloses의 발달, 내용물의 충진 혹은 천공판등이 관계하는 것으로 생각되고 있다. 6. 침엽수재 방사조직에 있어서는 방사유세포보다 방사가도관의 침투성이 양호하였으며 활엽수재의 방사조직은 구성비율이 높음에도 불구하고 단량체의 방사방향에 미치는 영향은 침엽수재보다 적었다. 7. 비중과 연륜폭은 모두 polymer의 침투성과 거의 관계가 없었다.