미세구조에 따른 La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ 분리막의 산소투과 및 기계적 특성

이시우,이승영,이기성,우상국,김도경,Lee, Shi-Woo,Lee, Seung-Young,Lee, Kee-Sung,Woo, Sang-Kuk,Kim, Do-Kyung 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10

고상 반응법을 통해 $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ 페롭스카이트계 산소투과 분리막을 제조하였으며, 미세구조에 따른 산소투과 특성 및 기계적 특성을 고찰하였다. 분리막의 미세구조는 소결온도 및 소결 유지시간을 달리함으로써 조절하였으며, 미세구조에 따른 평균 입경 및 상대밀도의 변화를 평가하였다. 입계 분율의 감소에 따라 산소투과유속이 증가하는 경향을 나타내었으며, 본 연구에서 고찰한 소결조건 중에서는 1300${\circ}C$에서 10시간 유지하여 제조한, 상대밀도가 높고 비교적 입경이 조대한 분리막 시편의 경우, 최대 0.37 ml/$cm^2$${\cdot}$min의 산소투과유속이 특정되었다. 파괴강도는 소결체의 상대밀도에 의존적이었으며, 파괴인성은 결정립의 크기에 따라 증가하는 경향을 나타내었다. Oxygen permeability and the mechanical properties of mixed ionic-electronic conductive $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ perovskite-type membrane, fabricated by solid state reaction, were investigated with regard to microstructure. The microstructure of the membrane was controlled by changing the sintering temperature and holding time. The average grain size and relative density were evaluated as a function of sintering conditions. As the fraction of grain boundary decreased, oxygen permeability showed a tendency to increase. Especially the maximum oxygen flux of 0.37 ml/$cm^2$${\cdot}$min was measured for the specimen sintered at 1300${\circ}C$ for 10 h, which has high density and relatively large grain size. Fracture strength was dependent on the relative density of sintered body, while fracture toughness increased with average grain size.

연구발표초록 ( 재료 ) : AlCl3 - NH3 반응에서 AlN 분말의 수율 및 특성

이시우,박종록,이건홍 ( Shi Woo Rhee,Jong Rock Park,Kun Hong Lee ) 한국화학공학회 1992 춘계학술발표회 Vol.- No.-

Dual Phase 전도성 CO₂ 분리막: 메커니즘, 미세구조 및 전기전도도

이시우,유지행,우상국,Lee, Shi-Woo,Yu, Ji-Haeng,Woo, Sang-Kuk 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.8

Novel conductive $CO_2$ membranes composed of dual phases, molten carbonates and electronic conducting ceramics, were investigated. As the microstructure control of electronic conducting ceramic supports is extremely important to keep the molten carbonates stable in the membranes by a capillary force applied by the pore structure of the supports, we have scrutinized the microstructure of the electronic conducting supports utilizing microscopic images and gas permeability measurement. From the evaluation of the electrical conductivities of the molten carbonates and the electronic conducting ceramic supports, we found that the ionic conductivity of the molten carbonates could determine $CO_2$ flux through the dual phase membranes if the surface exchange rate were relatively high enough.

혈관 내 미세 유체환경에서 혈관 내피 세포와 공배양된 중간엽 줄기세포의 특성 관찰

이시우 ( Shi Woo Lee ),장지연 ( Ji Yeon Jang ),박소희 ( So Hee Park ),김동화 ( Dong Hwa Kim ),신지원 ( Ji Won Shin ),김수향 ( Su Hyang Kim ),신정욱 ( Jung Woog Shin ) 한국조직공학과 재생의학회 2010 조직공학과 재생의학 Vol.7 No.2

In this study we investigated the effects of biochemical reagents, direct co-culturing as well as flowinduced shear stress on the differentiation of MSCs into vascular cell lineages. To investigate the effects of growth factors on the differentiation of MSCs, medium with/without growth factors were used. To induce shear stress by fluid-flow on the cells, miniature flow cell chips were fabricated using polydimethylsiloxane. For the co-cultures, MSCs were mixed with HUVECs in the ratio of 1:2. 48h after the seeding, the shear stress was imposed on the cells. The flow rate was adjusted to have the shear stress as 10 dyne/cm2. Immunofluorescence stainings for α-smooth muscle actin (α-SMA) and von Willebrand factor (vWF) were performed. Acquired stained samples from a confocal microscope were analyzed by image processing. Any expressions of vascular specific markers were not shown in MSCs co-cultured with HUVECs when growth factors were not added. The expressions of α-SMA were observed in MSCs co-cultured with growth factor under static culture on day 4, but these were remarkably decreased on day 7. The expressions of α-SMA in MSCs co-cultured under shear stress were increased regardless of the growth factor. The highest expression of α-SMA was observed in MSCs co-cultured with flow-induced shear stress. The expressions of vWF were not observed in MSCs in all groups. In summary, we have shown that coculturing of MSCs and HUVECs under shear stressing, which mimics micro-environments, could help MSCs differentiate toward smooth muscle like cells.

빛 공해 방지를 위한 유럽형 LED 가로등용 비구면 광학계에 관한 연구

이시우(Shi-Woo Lee),이창수(Chang-Soo Lee),현동훈(Dong-Hoon Hyun) 한국생산제조학회 2013 한국생산제조학회지 Vol.22 No.3

In this study, we researched a pendant-type aspherical optical system, which could be applied to street lighting and security lighting in Europe. The goal of this research was eco-friendly artificial lighting that could be used for the one-to-one replacement of ordinary lighting. LED lighting was miniaturized by using one COB LED Module and one aspherical optical system, which could control the luminosity of the LED. Through the aspherical optical system, the light distribution angle could be controlled in a range of 140° for the X-axis and 40° for the Y-axis. This means that this optical system is appropriate for catenary-type lighting, which is widely used in Europe on both narrow and broad roads. The performance was determined using a lighting simulation program. This lighting system simulation showed that road rates M4 and M5 could be satisfied, with the condition of a 13-m height and 50-m distance (U0 and TI). The simulation program estimated that light pollution, which disturbs sleep, could beeliminated in the European streetlight case. Determining methods for the light distribution control, performance, and optimal lighting setup conditions is very important to prevent light pollution. Moreover, the initial step of developing the lighting system design and post management will require an effort with much analysis.

형상이 제어된 골 조직 재생용 3차원 지지체를 적용한 새로운 형태의 Perfusion Culture

이시우 ( Shi Woo Lee ),허수진 ( Su Jin Heo ),장지연 ( Ji Yeon Jang ),정재영 ( Jae Young Jeong ),김수향 ( Su Hyang Kim ),박수아 ( Su A Park ),전은수 ( Eun Su Jeon ),신정욱 ( Jung Woog Shin ) 한국조직공학·재생의학회 2010 조직공학과 재생의학 Vol.7 No.1

The objective of this study was to investigate the efficacy of a newly designed perfusion bioreactor which provides flow-induced mechanical stimulation on the cells residing in the intra-morphology controllable scaffolds. For this, we fabricated scaffolds composed of poly e-caprolactone (PCL) and micro-sized hydroxyapatite (HA) particles using rapid-prototyping process. Also a new bioreactor system for perfusion culture was designed and developed. For the analyses of cellular responses of bone-tissue related cells cultured in the perfusion bioreactor system, various biological assays were performed such as MTT test, DNA content measurement, FE-SEM and live/dead staining. The cells used in this study were MG-63 (human osteoblast-like cell line) and mesenchymal stem cells from New Zealand white rabbits. Our results showed that the cells cultured by the perfusion bioreactor resulted in higher proliferation rate and mineralization of extracellular matrices than those cultured in static culture. From this study, we could confirm the potentials of 1) a newly developed perfusion bioreactor, 2) intra-morphology controllable scaffolds composed of PCL and HA particle and 3) the combination of the suggested scaffolds and perfusion culturing system in relation to bone tissue engineering.

고상반응에 의하여 제조된 Li₂ZrO₃의 이산화탄소 흡수 및 소결 특성

우상국,이시우,유지행,Woo, Sang-Kuk,Lee, Shi-Woo,Yu, Ji-Haeng 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.5

We synthesized lithium zirconate using solid-state reaction and analyzed thermal properties (TG/DTA) of starting materials and the synthesized one. When $Li_2ZrO_3$ powder was exposed to $CO_2$ environment at $500^{\circ}C$, 93% of the theoretical absorption weight was gained within 280 min with fairly high sorption rate. Almost all the absorbed $CO_2$ was generated by heating the sample to $800^{\circ}C$. We also investigated densification behavior of $Li_2ZrO_3$ under $CO_2$ environment. By sintering $Li_2ZrO_3$ at $760^{\circ}C$ using 2-step process, we obtained dense product, composed mainly of $Li_2ZrO_3\;and\;ZrO_2$, with relative density of 92%.

Chemical Vapor Deposition of Tungsten on TiN Surface

이청,이시우,이건홍,Yi, Chung,Rhee, Shi-Woo,Lee, Kun-Hong The Institute of Electronics and Information Engin 1992 전자공학회논문지-A Vol.29 No.4

Tungsten film was deposited on the TiN surface in a low pressure chemical vapor deposition reactor and chemical reaction mechanism between TiN surface and ($WF_{6}\;and\;SiH_{4}$ was studied. Interaction of ($WF_{6}\;or\;SiH_{4}$ with TiN surface and tungsten was deposited more easily. $WF_6$ reacted with TiN activated the TiN surface to form volatile TiF_4$ and tungsten nuclei were formed. ($SiH_{4}$ was dissociated on the TiN surface to form silicon nuclei. From RBS and AES analysis, we could not detect the impurities(such as Si or TiF$_x$)at the interface between tungsten and TiN. The adhesion at the W/TiN interface became poor when the deposition temperature was below 275$^{\circ}C$.

MOVCD에 있어서 구리(l)전구체들의 열적 안정성이 증착에 미치는 영향

박만영,이시우,Park, Man-Young,Lee, Shi-Woo 한국재료학회 1998 한국재료학회지 Vol.8 No.4

음이온 리간드로 hfac이 배위된 세 가지 종류의 구리(l) 전구체들의 열적 안정성, 기상분해 특성, 증착 특성 등을 연구하였다. $^{1}$H-NMR결과로부터 (hfac) Cu(VTMS) (hfac=hexafluoroacetylacetonate, VTMS=vinyltrimethylsilane)와 (hfac)Cu(VTMS) (VTMOS=vinyltrimethoxysilane)는 열적으로 안정한 화합물이라는 것을 확인할 수 있었으며, (hfac)Cu(ATMS)(STMS=allyltrimethylsilane)는 다른 전구체에 비해 열적으로 불안정한 화합물이라는 것을 확인할 수 있었다. In-situ FT-IR을 이용하여 기상 분해 특성을 연구한 결과 (hfac)Cu(VTMS)의 경우 $150^{\circ}C$부근에서 $Cu(hfac)_{2}$, $240^{\circ}C$부근에서 free한 상태의 hfac의 생성을 확인할 수 있었으며, 이러한 특성이 박막의 증착 속도와 물성에 미치는 영향을 확인하였다. 그리고 이들 전구체들의 증착 특성을 연구하였으며 (hfac)Cu(ATMS)의 경우 아르곤 운반 기체하에서 기판 온도가 $60^{\circ}C$일 때 구리 박막이 증착이 시작되는 것을 관찰할 수 있었는데, 이러한 낮은 증착 온도는 상대적으로 약한 구리와 ATMS의 결합력에 의한 것으로 생각된다. Metal organic chemical vapor deposition (MOCVD) of copper using three Cu( I ) precursors. (hfac)Cu (VTMS) (hfac= hexafluoroacetylacetonate, VTMS= vinyltrimethylsilane), (hfac)Cu(VTMOS) (VTMOS= vinyltri¬methoxysilane) and (hfac)Cu(A TMS) (A TMS= allyltrimethylsilane) was studied. The thermal stability and the gase¬ous phase reaction mechanism of Cu( I ) precursors were identified using $^1H$-, $^I3C$-NMR and Fourier transform infra¬red spectroscopy. It was found out that thermal stability of liquid phase (hfac)Cu(VTMS) and (hfac)Cu(VTMOS) were better than that of (hfac)Cu(A TMS) using FT - NMR. From in-situ FT - IR experiments, the disproportion reaction of Cu(hfac). the decomposition reaction of Cu(hfac), and cracking of free hfac ligand were observed. Also the effect of gaseous phase reaction on the deposition rates and film properties was investigated. The minimum temperature that deposition of copper films from (hfac)Cu(A TMS) was as low as 60$^{\circ}$C and such a low deposition temperature compared with those of other Cu( I ) precursors is believed to be related with weaken Cu- A TMS bond.

Li₂ZrO₃ 분리막의 제조와 이산화탄소 선택투과 전후의 기계적 특성 평가

박상현,이시우,유지행,우상국,이기성,Park, Sang-Hyun,Lee, Shi-Woo,Yu, Ji-Haeng,Woo, Sang-Kuk,Lee, Kee-Sung 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.1

In this study, we investigated $Li_2ZrO_3$ membrane as a candidate material for high-temperature $CO_2$ separation and evaluated mechanical property. $Li_2ZrO_3$ powder was synthesized by solid state reaction of $Li_2CO_3\;and\;ZrO_2$. Then we fabricated $Li_2ZrO_3$ tape using tape casting method. Dense $Li_2ZrO_3$ membrane prepared by sintering at $1600^{\circ}C$ for 2 h after pressing $Li_2ZrO_3$ tape using lamination machine. Mechanical properties before and after $CO_2$ absorption of fabricated $Li_2ZrO_3$ membrane such as Hertzian indentation, Victors hardness and 3-point bending testing were evaluated.