• Title/Summary/Keyword: 유리상전이

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Preparation and Radionuclide Detection Analysis of Inorganic Fluor Impregnated Double-layered Membranes (이중구조 무기형광 함침막 제조 및 방사성핵종 탐지능력의 분석)

  • 이근우;서범경;박진호;남석태;한명진
    • Membrane Journal
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    • v.12 no.4
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    • pp.240-246
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    • 2002
  • New polysulfone scintillation proximity membranes were prepared by impregnating Cerium Activated Yttrium Silicate (CAYS), an inorganic fluor, in a membrane structure. The membranes were applied to detect the radionuclide contamination directly without the aid of a scintillation cocktail. The preparation of membranes was divided into two processes. A supporting polymer film was made of casting solutions consisting of polysulfone and solvent, their cast film being solidified by vacuum evaporation. CAYS-dispersed polymer solutions were cast over the first, solidified polymer films and coagulated either by evaporating solvent or by exchanging solvent in the solution with nonsolvent in a coagulation bath. The prepared membranes had two distinguished, but tight1y attached, double layers: one is the supporting layer of dense polymer film and the other the detecting layer consisting of CAYS and polymer. The radionuclide counting results revealed that the prepared membranes were efficient to monitor radioactivity contamination with reliable counting ability.

Preparation of Au fine particle dispersedf $TiO_{2}$ film by sol-gel and photoreduction process (Sol-Gel and photoreduction 공정에 의한 Au 미립자분산 $TiO_{2}$ 박막 제조)

  • 현부성;김병일;강원호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.1
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    • pp.23-28
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    • 1999
  • Au fine particles dispersed $TiO_{2}$ film was prepared on silica glass substrate by sol-gel dipping and firing process. The $TiO_{2}$ films were fabricated from the system of titanium tetraisopropoxide-EtOH-HCl-$H_{2}O$-hydrogen tetrachloroaurat (III) tetrahydrate. The conditions for the formation of clear solution and dissolving high concentration of Au compound were examined. Photoreduction process was adopted to control the size of gold metal particles. Phase evolution of matrix $TiO_{2}$ and variation of Au particle with UV irradiation were investigated by XRD, SEM, TEM and UV-visible spectrophotometer. The effect of CPCl (Cetylpyridinium chloride monohydrate) as a dispersion agent was evaluated.

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A study on properties and phase change characteristics of $Ga_x(Ge_2Sb_2Te_5)_{1-x}$ (x=0, 0.05, 0.1) thin films ($Ga_x(Ge_2Sb_2Te_5)_{1-x}$ (x=0, 0.05, 0.1) 박막의 물성 및 상변화 특성 평가)

  • Han, Gwang-Min;Song, Ki-Ho;Beak, Seung-Cheol;Lee, Hyun-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.103-103
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    • 2009
  • 본 논문에서는 기존의 GST(GeSbTe=2:2:5)와 비교하여 상변화 재료로서의 Ga 도핑된 $Ge_2Sb_2Te_5$의 가능성을 확인하고자 하였다. 실험에 사용된 Ga 도핑된 $Ge_2Sb_2Te_5$ 박막은 전통적 melt-quenching 방법에 의해 비정질로 제작된 벌크를 Thermal evaporation을 통하여 Si(100) 및 유리 (coming glass, 7059) 기판 위에 200nm의 두께로 증착하여 제작하였다. 각 박막의 상변화 특성은 여러 온도에서 열처리된 박막을 X-ray diffraction (XRD) 측정을 통하여 확인하였다. 각 조성 박막의 비정질-결정질 상변화속도 비교를 위하여 나노-펄스 스캐너 (nano-pulse scanner)를 사용하여 power; 1~17mW, pulse duration; 10~460ns 범위에서 박막의 상변화에 따른 반사도 차이를 측정 분석하였다. Ga의 도핑농도에 따른 전기적 특성 차이를 확인하기 위하여 4-point probe를 이용하여 박막의 면 저항을 측정하였고 또한 hall 측정을 통하여 박막의 흘 계수, 흘 농도 및 이동도를 확인하고 Ga가 상전이에 미치는 영향에 대하여 분석하였다.

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Thermotropic Liquid Crystalline and Photochemical Phase Transition Behavior of Octa[8-{4-(4'-cyanophenylazo)phenoxy}]octyl and Octa[8-{4-(4'-cyanophenylazo) phenoxycarbonyl}]heptanoated Disaccharides (옥타[8-{4-(4'-시아노페닐아조)펜옥시}]옥틸 그리고 옥타[8-{4-(4'-시아노페닐아조) 펜옥시카보닐}]헵타노화 이당류의 열방성 액정과 광화학적 상전이 거동)

  • Kim, Hyo Gap;Jung, Seung Yong;Jeong, Hee Sung;Ma, Yung Dae
    • Polymer(Korea)
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    • v.36 no.6
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    • pp.776-788
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    • 2012
  • Octa[8-{4-(4'-cyanophenylazo)phenoxy}]octyl and octa[8-{4-(4'-cyanophenylazo)phenoxycarbonyl}]heptanoated disaccharide derivatives were synthesized by reacting cellobiose, maltose, and lactose with 1-{4-(4'-cyanophenylazo) phenoxy}octylbromide or 1-{4-(4'-cyanophenylazo)phenoxycarbonyl}]heptanoyl chloride, and their thermotropic liquid crystalline and photochemical phase transition behavior were investigated. All the {(cyanophenylazo)phenoxy} octyl disaccharide ethers (CADETs) formed monotropic nematic (N) phases, whereas all the {(cyanophenylazo) phenoxycarbonyl}heptanoated disaccharide esters (CADESs) exhibited enantiotropic N phases. Compared with CADETs, CADESs showed higher isotropic (I)-to-N phase transition temperatures. Photoirradiation of the disaccharide derivatives in a glass cell or in a cell with a rubbed polyimide (PI) alignment layer at a N phase resulted in disappearance of the N phase due to trans-cis photoisomerization of azobenzene, and the initial N phase was recovered when the irradiated sample was kept in the dark because of cis-trans thermal isomerization and reorientation of trans-azobenzenes. The rates of the photochemical N-I and the thermal I-N phase transition of disaccharide derivatives in a cell with a rubbed PI alignment layer were faster than those in a glass cell, and were significantly different from those observed for the monomesogenic compounds containing cyanoazobenzene and the 4-{4'-(cyanophenylazo)phenoxy}octyl glucose and cellulose ethers. The results were discussed in terms of difference in cooperative motion of azobenzene groups due to the flexibility of the main chain, the number of mesogenic units per repeating units, and the distance between the azobenzene groups.

Development of U-shaped Arterialvenous Shunt Using Porous Polyurethane (다공성 폴리우레탄을 이용한 동정맥 누관의 개발)

  • 정재승;김희찬;박광석;최진욱;민병구
    • Journal of Biomedical Engineering Research
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    • v.20 no.2
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    • pp.221-230
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    • 1999
  • A new technique for the preparation of porous polyurethane vascular prostheses was investigated. Synthetic vascular grafts with porous wall have been widely proposed, claiming that strength, suture retention, kink resistance, and other handling properties are improved over those with nonporous solid wall. Related to these facts, the control of pores and compliance match have been very important and interesting issues. Two kinds of polymer sheets were compared. One was the porous PU-sheet made at room temerature by the solvent/non-solvent exchange. And the other was the porous PU-sheet fabricated by thermal phase transition and solvent/non-solvent exchange in the thermal controlled bath. According to the result of the above experiments, polyurethane solution was injected into a mold designed for U-type graft. After freezing at low temperature, solvent was dissolved out with alcohol at < $0^{\circ}C$ and water at room temperature to form porous vessels. The average pore size and pore occupation were easily changed by changing polyurethane concentration and freezing rate. This technique can give a proper pore size for tissue ingrowth, and suitable compliances for matching with arteries and veins. In addition, the fabrication of more complicated shaped vessels such as the U-type vascular grafts is easily controlled by using a mold. This method might give a desired compliact graft for artificial implantaion with the commercially available medical polymers.

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Preparation and Characterization of Microporous PVdF Membrane for Li-ion Rechargeable Battery (이차전지용 미세다공성 PVdF 분리막의 제조와 물성)

  • Nam, Sang-Yong;Yu, Dae-Hyun;Jeong, Mi-Ae;Rhim, Ji-Won;Byun, Hong-Sik;Jeong, Chul-Ho;Lee, Young-Moo;Seo, Myung-Su
    • Membrane Journal
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    • v.17 no.3
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    • pp.233-243
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    • 2007
  • In this study, a separate. which is a microporous membrane based on poly(vinylidene fluoride)(PVdF) was prepared by phase inversion method. Being prepared by dissolving the PVdF in the N,N'-dimethylformamide(DMF) with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Pore size and porosity of the membranes were controlled by changing preparation condition. The highest porosity of the membrane was 78.6%. The mechanical property of the membrane was determined by using an universal testing machine(UTM). The morphology of the membrane was investigated by scanning electron microscopy(SEM). The cross-section of the membrane shows sponge-like small micro-pores.

The Scientific Analysis of Floor Tile Excavated from the Beobgwangsa Temple Site in the Pohang (포항 법광사지 출토 녹유전의 자연 과학적 조사)

  • Moon Whan-Suk;Han Min-Su;Hwang Jin-Ju;Kim Ho-Sang
    • KOMUNHWA
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    • no.60
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    • pp.101-120
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    • 2002
  • The floor tile on a coated green-glass was excavated from the Beobgwangsa Temple Site in the Pohang City. We analyzed using the MXRD, ICP-AES, EDXRF, TG/DTA and TIMS. As a result of microscope analysis, it was composed of quartz, feldspar and clay particl

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Preparation and Characterization of PVdF-HFP Microporous Membranes for Li-ion Rechargeable Battery (Poly(vinylidene fluoride-hexafluoropropylene)를 이용한 이차전지용 미세다공성 분리막의 제조와 물성)

  • Nam, Sang-Yong;Yu, Dae-Hyun;Jeong, Mi-Ae;Rhim, Ji-Won;Byun, Hong-Sik;Yoo, Hyun-Oh;Kim, Jong-Man;Seo, Myung-Su
    • Membrane Journal
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    • v.17 no.4
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    • pp.359-368
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    • 2007
  • The copolymer membranes, poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by phase inversion method using as an additive with N,N-dimethylformamid as a solvent. The pores are generated during the solvent and non-solvent exchange process in the coagulation bath filled with non-solvent (distilled water). The highest porosity of the membrane was 60%. The surface and cross-section of the membranes was observed with a scanning electron microscopy (SEM). The mechanical property of the membrane was determined by using an universal testing machine (UTM). Tensile strength of measured membranes is presented the maximum 6.57 MPa at 30 wt% of PVdF-HFP.

Color Evolution and Phase Transformation of α-FeOOH@SiO2 and β-FeOOH@SiO2 pigments (SiO2가 코팅된 α-FeOOH와 β-FeOOH의 상전이를 통한 SiO2가 코팅된 α-Fe2O3의 색상 연구)

  • Yu, Ri;Choi, Kyoon;Pee, Jae-Hwan;Kim, YooJin
    • Journal of Powder Materials
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    • v.20 no.3
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    • pp.210-214
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    • 2013
  • This manuscript reports on compared color evolution about phase transformation of ${\alpha}-FeOOH@SiO_2$ and ${\beta}-FeOOH@SiO_2$ pigments. Prepared ${\alpha}$-FeOOH and ${\beta}$-FeOOH were coated with silica for enhancing thermal properties and coloration of both samples. To study phase and color of ${\alpha}$-FeOOH and ${\beta}$-FeOOH, we prepared nano sized iron oxide hydroxide pigments which were coated with $SiO_2$ using tetraethylorthosilicate and cetyltrimethyl-ammonium bromide as a surface modifier. The silica-coated both samples were calcined at high temperatures (300, 700 and $1000^{\circ}C$) and characterized by scanning electron microscopy, CIE $L^*a^*b^*$ color parameter measurements, transmission electron microscopy and UV-vis spectroscopy. The yellow ${\alpha}$-FeOOH and ${\beta}$-FeOOH was transformed to ${\alpha}-Fe_2O_3$ with red, brown at 300, $700^{\circ}C$, respectively.

A Study on Electrical Conduction of As-Te-Si-Ge Amorphous Semiconductor (As-Te-Si-Ge 유리질 반도체의 전기전도에 관한 연구)

  • Park, Chang-Yeub;Wang, Jin-Seok;Jeong, Hong-Bae
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.12 no.2
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    • pp.18-23
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    • 1975
  • The dc conductivity, ac conductivity and switching effect of As.Te-Si.Ge have beon investigated. The dc conductivity ranged from $3{\times}10^{-7}{\Omega}^{-1}cm^{-1}$ to $1.5{\times}10^{-8}{\Omega}^{-1}cm^{-1}$ at room temperature and was found to be expressed by ${\sigma}$ = ${\sigma}_0$exp(-${\Delta}$E/kT) below the phase transition temperature Tg. The ac conductivity was much higher than dc conductivity and this result is consistent to experimental formula ${\sigma}$(w)=${\sigma}_0+Aw^n$. In the temperature range of 298$^{\circ}K$ ~ $473^{\circ}K$ the ac conductivity was independent of temperature at 200KHs. At lower frequencies the ac conductivity increased strong1y with temperature. Also, it has been found that all samples showed a threshold switching, but not a memory switching.

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