• Progress in Superconductivity
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• 제7권2호
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• pp.140-144
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• 2006

We fabricated the YBCO films on single crystal $LaAlO_3$ substrates via a metal organic deposition (MOD) process. In the process, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were dissolved in trifluoroacetic acid (TFA) followed by calcining and firing heat treatments. To evaluate the effects of the firing temperature on YBCO phase formation and critical properties, the films were fired at $750^{\circ}C,\;775^{\circ}C\;and\;800^{\circ}C$ after calcining at $430^{\cric}C$. Microstructure observation indicated that a crack-free surface formed and a strong biaxial texture was developed. The FWHM of out-of-plane texture was measured to be in the range of $4.3^{\cric}-7.0^{\circ}$ for all the films. When the YBCO film was fired at $775^{\cric}C$, it had the highest critical properties: 88.5 K of critical temperature and 16 A/cm-width of critical current ($1MA/cm^2$ as critical current density). On the other hand, those properties were degraded as firing at $750^{\circ}C\;and\;800^{\circ}C$. It is considered that the improved critical values are partly owing to dense and homogeneous microstructure, strong texture, and high oxygen content.

• Journal of Information Display
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• 제5권1호
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• pp.28-33
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• 2004

A high voltage NMOSFET is proposed to drive top emission organic light emitting device (OLED) used in the organic electroluminescent (EL) display on the single crystal silicon substrate. The high voltage NMOSFET can be fabricated by utilizing a simple layout technique with a standard CMOS logic process. It is clearly shown that the maximum supply voltage ($V_{DD}$) required for the pixel-driving transistor could reach 45 V through analytic and experimental methods. The high voltage NMOSFET was fabricated by using a standard 1.5 ${\mu}m$, 5 V CMOS logic process. From the measurements, we confirmed that the high voltage NMOSFET could sustain the excellent saturation characteristic up to 50 V without breakdown phenomena.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.728-734
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• 2011

$LiFePO_4$ is a promising cathode material for secondary lithium batteries due to its high energy density, low cost and safety. $LiFePO_4$ was synthesized by the citrate process under reductive, neutral, and oxidative, atmospheres and the crystal structure was analyzed by X-ray powder diffraction. The samples synthesized under $N_2$ and $H_2$ atmosphere showed a single phase of a olivine structure, where the samples synthesized under $O_2$ atmosphere exhibited second phase of $Fe2O_3$. All the samples synthesized at 400, 600 and $800^{\circ}C$ under $N_2$ atmosphere presented a single phase of olivine. Residual organic material was observed for the sample synthesized at $400^{\circ}C$. There was nearly no intensity difference between the samples synthesized at $600^{\circ}C$ and $800^{\circ}C$. The electrochemical characteristic of the $LiFePO_4$ synthesized at $600^{\circ}C$ in the $N_2$ atmosphere was analyzed. The result exhibited an high discharge capacity of 160 mAh/g at the first cycle, and 155-160 mAh/g after 45 cycles.

• 공업화학
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• 제10권1호
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• pp.105-111
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• 1999

현재 iron silicide막을 제작하고 있는 방법은 열처리를 수행함으로써 막의 계면 상태가 좋지 않으나 플라즈마를 이용하였을 때는 열처리를 수행하지 않으므로 양질의 막을 얻을 수 있다. 본 실험에서 제작된 막은 Raman 스펙트럼 $250cm^{-1}$에서 나타난 Fe와 Si의 진동모드와 FT-IR에 의해 유기화합물 뿐만 아니라 Fe-Si의 결합이 형성되었음을 확인하였다. 또한 플라즈마의 높은 에너지에 의해 낮은 기판 온도에서 에피택시 성장이 진행되는 동안 iron silicide는 [220]/[202], [115] 등과 같은 격자구조를 갖는 ${\beta}$-상으로 성장하였다. 제조된 막의 band gap은 1.182~1.174 eV의 값을 가지고, 광학적 에너지갭을 3.4~3.7 eV의 값을 나타내었다. 막 내의 유기화합물에 의해 유발되는 Urbach tail과 sub-band-gap 흡수가 관측되었다. 따라서 플라즈마를 이용하여 제작된 막은 단일결정이 성장되어 양질의 박막을 얻을 수 있음을 확인하였다.

• 공업화학
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• 제20권3호
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• pp.335-338
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• 2009

유기발광다이오드의 청색 발광 물질로 많은 관심을 받고 있는 디스티릴아릴렌 화합물들의 합성 과정에서 핵심적인 중간체인 브로모트리페닐에틸렌 화합물들은 브로모벤조페논과 벤질포스포네이트의 반응을 통하여 얻어진다. 이 반응은 분리하기 어려운 (Z)-와 (E)-기하이성질체가 60 : 40의 비율로 생성한다. 본 연구에서는 2-프로탄올을 이용한 재결정법을 통하여 (Z)-이성질체를 간단하게 분리하였다. X-ray를 이용하여 (Z)-이성질체의 결정 구조를 살펴본 결과, tert-부틸페닐 고리와 브로모페닐 고리 간의 dihedral angle은 $56.5(4)^{\circ}$이며 브로모페닐 고리와 페닐 고리 간의 dihedral angle은 $74.1(4)^{\circ}$였다.

• 한국재료학회지
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• 제15권3호
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• pp.177-182
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• 2005

Large amounts of the waste SiC sludge containing small amounts of Si and organic lubricant were produced during the wire cutting process of the single silicon crystal ingots. The waste SiC sludge was purified by the washing process and the purified SiC powders were used to fabricate continuously porous $SiC-Si_3N_4$ composites using a fibrous monolithic process, in which carbon, $6wt\%\;Y_2O_3-2\;wt\%\;A1_2O_3$ and ethylene vinyl acetate were added as a pore-forming agent, sintering additives, and binder, respectively. In the burning-out process, carbon was fully removed and continuously porous $SiC-Si_3N_4$ composites were successfully fabricated. The green bodies containing SiC, Si particles and sintering additives were nitrided at $1410^{\circ}C$ in a flowing $N_2+10\%\;H_2$ gas mixture. Continuously porous composites were combined with SiC, ${\alpha}Si_3N_4,\;\beta-Si_3N_4$ and a few $\%$ of Fe phases. The pore size of the 2nd and the 3rd passed $SiC-Si_3N_4$ composites was $260\;{\mu}m$ and $35\;{\mu}m$ in diameter, respectively.

• 대한화학회지
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• 제40권1호
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• pp.65-71
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• 1996

유기 리간드(tris[3-(trifluoromethylhydroxymethymelene-camphorato])와 tris[3-(heptafluoropropylhydroxymethymelene-camphorato])을 Eu(Ⅲ)와의 착물들에 대한 거동을 UV-vis 분광학적, 자기적, 그리고 전기화학적 방법에 의해 조사하였다. 둘 또는 세개의 에너지 흡수 띠가 이들 착물들의 스펙트라에 의해 관찰되었다. 결정장 갈라짐 에너지 크기와 스핀 짝지움 에너지 그리고 결합 세기는 착물들의 스펙트라로부터 얻어졌다. 이들 착물은 전자 배열이 비 편재화이고, 낮은 스핀 상태이며 그리고 강한 결합 세기임을 알았다. 자기 쌍극자 모멘트는 반 자기성 착물로 나타났다. 착물들의 산화.환원 과정은 반 양성자성 용매속에서 순환 전압 전류법에 의해서 조사하였다. 착물들의 산화.환원 과정은 일전자의 확산전류에 의한 단일-짝 반응이었다.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2351-2357
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• 2011

Three new metal-organic copper(II) complexes, $[Cu(H_2PZTC)_2]_n{\cdot}2nH_2O$ (1), $[Cu(HPZTC){\cdot}2H_2O]_n{\cdot}2nH_2O$ (2), and $Cu_2[(PZHD)(OH)(H_2O)_2]_n$ (3) ($H_3PZTC$ = pyrazine-2,3,5-tricarboxylic acid, $PZHD^{3-}$ = 2-hydroxypyrazine-3,5-dicarboxylate), have been synthesized from $Cu(II)/H_3PZTC$ system under different synthetic conditions, and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. In complexes 1 and 2, $H_3PZTC$ ligands loose one and two protons, which were transformed into $H_2PZTC^-$ anion and $HPZTC^{2-}$ dianion under different preparation condition, respectively. Furthermore, two ligands coordinate with Cu(II) cations in different modes, leading to the formation of the different chain structures. In complex 3, $H_3PZTC$ ligand was converted into a new ligand-PZHD by in situ decarboxylation and hydroxylation under a higher pH value than that for complexes 1 and 2. PZHD ligands link the Cu(II) cations to form a 2D layer structure. These results demonstrate that the preparation conditions, including pH value and reaction temperature etc, play an important role in the construction of complexes based on $H_3PZTC$ ligand.

• Progress in Superconductivity
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• 제8권1호
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• pp.75-80
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• 2006

[ $Yb_2O_3$ ] films were successfully deposited on a cube-textured Ni and(100) $SrTiO_3$(STO) single crystal substrates by metal organic chemical vapor deposition(MOCVD) method using $H_2O$ vapor as an oxidant. $H_2O$ vapor was used in order to avoid the oxidation of Ni substrate. The working pressure and Ar flow rate were 10 Ton and 600 sccm, respectively. $Yb_2O_3$ films on STO were formed at high temperatures above $900^{\circ}C$. While XRD peaks from $Yb_2O_3$ were hardly detected at $900^{\circ}C$, the $Yb_2O_3$(400) texture was developed fur the films grown at deposition temperatures above $950^{\circ}C$. The AEM surface roughness of $Yb_2O_3$ film, grown on STO, was in the range of $6{\sim}10nm$ for the film deposited at $950^{\circ}C$ with a $H_2O$ vapor partial pressure of 5.5 Ton and deposition times of 3 and 5 mins. For cube-textured Ni substrate, both $Yb_2O_3$(222) and $Yb_2O_3$ (400) textures were developed textures at deposition temperatures above $850^{\circ}C$.

• 설비공학논문집
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• 제20권4호
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• pp.266-273
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• 2008

Natural gas hydrates are ice-like solid substances, which are composed of water and natural gas, mainly methane. They have three kinds of crystal structures of five polyhedra formed by hydrogen-bonded water molecules, and are stable at high pressures and low temperatures. They contain large amounts of organic carbon and widely occur in deep oceans and permafrost regions. Therefore, they are expected as a potential energy resource in the future. Especially, $1m^3$ natural gas hydrate contains up to $172Nm^3$ of methane gas, de pending on the pressure and temperature of production. Such large volumes make natural gas hydrates can be used to store and transport natural gas. In this study, three-phase equilibrium conditions for forming natural gas hydrate were numerically obtained in pure water and single electrolyte solution containing 3 wt% NaCl. The results show that the predictions match the previous experimental values very well, and it was found that NaCl acts as an inhibitor. Also, help gases such that ethane, propane, i-butane, and n-butane reduce the hydrate formation pressure at the same temperature.