• 한국전기전자재료학회논문지
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• 제25권9호
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• pp.717-722
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• 2012

In this work, we study on the effects of the oxygen pressure on the structural and crystalline of MgZnO thin films. MgZnO thin films were deposited on p-Si (111) substrates by using pulsed laser deposition. The X-ray diffraction analysis and energy-dispersive X-ray results revealed that as the oxygen pressure increased and Mg content in the MgZnO films decreased. Also Crystal structure was changed from cubic rock salt to hexagonal wurtzite. Alpha step and atomic force microscopy results showed that the thickness of the films are about 100 nm, and it has been found that the MgZnO (002) preferred orientation were deposited with increasing the oxygen pressure. Therefore, the effect of the preferred orientation, the crystallization grew in the form of the columnar; Grain size and RMS of the films were increased with increasing oxygen pressure.

• Composites Research
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• 제28권3호
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• pp.75-80
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• 2015

Poly(vinylidene fluoride-trifluoroethylene; P(VDF-TrFE))는 여러 분야에서 다양한 형태로 활용되고 있는 유망한 전기활성고분자이다. 이 재료는 전기-기계적 특성을 가지고 있기 때문에 다양한 형태의 센서와 구동기로 활용되고 있으며, 복합재료 구조의 거동을 관찰하는 센서로도 활용이 가능하다. 본 논문에서는 세 가지 방법; (1) 전기적 폴링, (2) 어닐링-냉각, (3) 압축을 사용하여 P(VDF-TrFE) 공중합체 필름의 ${\beta}$ 상 결정구조 향상시켜 센서로서의 특성을 강화하기 위한 연구를 수행하였다. P(VDF-TrFE) 필름에 대한 각 방법의 효과를 조사하기 위해 X-선 회절을 통한 미세구조분석을 수행하였다. 실험 결과, 전기적 폴링, 어닐링-냉각, 그리고 압축 방법 모두 P(VDF-TrFE) 필름의 ${\beta}$ 상 결정구조 향상에 효과적이었으며 대조군 (45.29%)대비 최대 62.80%까지 ${\beta}$ 상 결정도가 향상됐다.

• 한국항해항만학회지
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• 제26권1호
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• pp.120-126
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• 2002

ZnS 박막을 Hot W긴 법에 의해 증발관 온도, 기판온도 및 외부로부터 유황(5)의 공급을 변수로 하여 제작하여 광학적, 결정 구조적 특성을 분석 ·검토하였다 박막의 증착속도는 증발관 온도 및 5 증기압을 높일수록 증가하였으나 기관온도를 높이면 급격히 감소하였다. 박막의 광학적 특성은 증착속도와 밀접하게 관계하고 있다고 사료되며, 실온에서의 금지대 폭은 이론 값보다 작은 3.46∼3.72ev를 나타내어 결정 중에 결함이 존재함을 알 수 있었다. 박막의 구조를 분석한 결과 어느 경우에 있어서나 섬아연광 구조의 (111) 주 배향성을 나타내었으나 회절피크의 강도 및 반치폭으로부터 결정성은 대체로 양호하지 못했음을 알았다. 그러나, 기판온도 또는 5 공급 등의 제작조건에 따라 광학적, 결정적 특성이 개선되었다.

• 미생물학회지
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• 제42권4호
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• pp.294-298
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• 2006

Streptomyces somaliensis가 생산하는 phospholipase D (PLD)를 정제하기 위하여 펩티드 항체 결합 면역 친화 크로마토그래피용 칼럼을 개발하였다. 단백질 구조 예측 프로그램과 Streptomyces PLD X-선 결정구조를 참조하여, S. somaliensis PLD의 1차 구조로부터 항원특성이 높고. 표면에 위치하는 것으로 예상된 5종류의 펩티드들을 epitope로 선정한 뒤, 이에 대한 항체로 면역친화 크로마토그래피용 칼럼을 제작하였다. 배양 농축액을 칼럼에 통과시켜 정제한 활성 분획을 SDS-PAGE 및 Western blot 결과, 칼럼 종류에 따라 순수한 PLD또는 35 kDa의 단백질 불순물만을 포함하는 PLD 정제 분획을 보여 면역친화 칼럼의 높은 항원결합 특이성을 보여주었다. 그러나 수용액상에서 PLD 자체의 구조적 불안정성 때문에 정제 후 PLD의 특이적 활성 및 정제 수율은 낮았다.

• 한국자기학회지
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• 제15권2호
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• pp.96-99
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• 2005

Phase transition from normal- to inverse-spinel structure has been observed for $Fe_xCo_{3-x}O_4$ thin films as the Fe composition (x) increases from 0 to 2. The samples were fabricated as thin films by sol-gel method on Si(100) substrates. X-ray diffraction measurements revealed a coexistence of two phases, normal and inverse spinel, for $0.76{\le}x{\le}0.93$. The normal-spinel phase is dominant for $x{\le}0.55$ while the inverse-spinel phase for $x{\ge}l.22$. The cubic lattice constant of the inverse-spinel phase is larger than that of the normal-spinel phase. For both phases the lattice constant increases with increasing x. X-ray photoelectron spectroscopy measurements revealed that both $Fe^{2+}$ and $Fe^{3+}$ ions exist with similar strength in the x=0.93 sample. Conversion electron $M\ddot{o}ssbauer$ spectra measured on the same sample showed that $Fe^{2+}$ ions prefer the octahedral $Co^{3+}$ sites, indicating the formation of the inverse-spinel phase. Analysis on the measured optical absorption spectra for the samples by spectroscopic ellipsometry indicates the dominance of the normal spinel phase for low x in which $Fe^{3+}$ ions tend to substitute the octahedral sites.

• 한국광학회지
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• 제16권3호
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• pp.201-208
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• 2005

조명각 변조 방식에 의한 3차원 입체영상 표시장치의 구현을 위해 렌티큘라 렌즈가 만족해야할 조건을 확립한 후 근축광선이론으로 렌즈 규격 및 모듈 구조를 설계하였고, 유한광선 추적법(finite ray tracing)을 이용하여 스테레오스코픽 모듈의 규격변화, 조립과정의 정렬오차, 그리고 관찰자의 관찰 조건에 따른 영향을 분석하였다. 이를 통해 신호잡음을 최소화하기 위해 제작 공정에서 렌즈 함몰부가 발생하지 않아야 하며, 평판형 액정 셔터와 렌티큘라 렌즈 판 사이의 어긋남이 최소화되어야 함을 알 수 있었다.

• 전기학회논문지P
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• 제57권2호
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• pp.140-145
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• 2008

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, ${\beta}-PVF_2$) organic thin films using the vapor deposition method. Vapor deposition was performed under the following conditions: the temperature of evaporator, the applied electric field, and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm, and $2.0{\times}10^{-5}\;Torr$, respectively. The molecular structure of the evaporated organic thin films were evaluated by a FT-IR. The results showed that the characteristic absorption peaks of $\beta$-form crystal increase from 72% to 95.5% with an increase in the substrate temperature. In the analysis of the electric characteristics, the abnormal increases in the relative dielectric constant and the dielectric loss factor in the regions of low frequency and high temperature are known to be caused by inclusion of impurity carriers in the PVDF organic thin films. In order to analyze quantitatively the abnormalities in the conductivity mechanism caused by ionic impurities, the product of the ion density and the mobility that affect the electrical property in polymeric insulators is analyzed. In the case of a specimen produced by varying the substrate temperature from $30^{\circ}C$ to $105^{\circ}C$, the product of mobility and the ion density decreased from $4.626{\times}10^8$ to $8.47{\times}10^7/V{\cdot}cm{\cdot}s$. This result suggests that the higher the substrate temperature is maintained, the better excluded the impurities are, and the more electrically stable material can be obtained.

• 한국재료학회지
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• 제19권12호
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• pp.667-673
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• 2009

The electrocatalytic characteristics of oxygen reduction reaction of the $PtxM_{(1-x)}$ (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The $Pt_xM_{(1-x)}$/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the $Pt_xM_{(1-x)}$ particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and $Pt_xM_{(1-x)}$/MWNTs catalysts are seen as FCC, and synthesized $Pt_xM_{(1-x)}$ crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, $Pt_{0.77}Co_{0.23}$/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or $Pt_xM_{(1-x)}$/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and $Pt_xM_{(1-x)}$ (M = Co, Cu, Ni) catalysts, the $Pt_{0.77}Co_{0.23}$/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.

• 한국재료학회지
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• 제22권10호
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• pp.504-507
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• 2012

Synthesis of RGO (reduced graphene oxide)-CdS composite material was performed through CBD (chemical bath deposition) method in which graphene oxide served as the support and Cadmium Sulfate Hydrate as the starting material. Graphene-based semiconductor photocatalysts have attracted extensive attention due to their usefulness for environmental and energy applications. The band gap (2.4 eV) of CdS corresponds well with the spectrum of sunlight because the crystalline phase, size, morphology, specic surface area and defects, etc., of CdS can affect its photocatalytic activity. The specific surface structure (morphology) of the photocatalyst can be effective for the suppression of recombination between photogenerated electrons and holes. Graphene (GN) has unique properties such as a high value of Young's modulus, large theoretical specific surface area, excellent thermal conductivity, high mobility of charge carriers, and good optical transmittance. These excellent properties make GN an ideal building block in nanocomposites. It can act as an excellent electron-acceptor/transport material. Therefore, the morphology, structural characterization and crystal structure were observed using various analytical tools, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. From this analysis, it is shown that CdS particles were well dispersed uniformly in the RGO sheet. Furthermore, the photocatalytic property of the resulting RGO-CdS composite is also discussed in relation to environmental applications such as the photocatalytic degradation of pollutants. It was found that the prepared RGO-CdS nanocomposites exhibited enhanced photocatalytic activity as compared with that of CdS nanoparticles. Therefore, better efficiency of photodegradation was found for water purification applications using RGO-CdS composite.

• 공업화학
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• 제23권2호
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• pp.138-142
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• 2012

블루 안료 15 : 6이라 불리는 ${\epsilon}$ 결정상의 동프탈로시아닌(${\epsilon}$-CuPc)는 LCD 패널에서 청색화소를 제공하는 중요한 소재로써, 본 연구에서는 ${\epsilon}$-CuPc 시료를 ${\epsilon}$-CuPc 나노 입자를 seed로 이용하는 방법으로 여러 조건에서 합성하여 적합한 용매 및 온도조건 등을 규명하였고, 이를 미리 합성한 ${\alpha}$ 및 ${\beta}$ 결정상의 CuPc 시료들과 비교함으로써 ${\epsilon}$-CuPc 시료의 결정상, 결정 순도, 합성 수율 및 미세구조를 상호 비교 분석하였다. 시료들의 화학 구조 및 결정 구조는 푸레어 변환 적외선(FT-IR) 분광기 및 X선 회절 분석기(XRD)를 이용하여 각각 비교 분석하였다. 또한, 입자의 형상 및 크기는 주사 전자현미경(FE-SEM)으로 비교 분석하였고, 열적 특성은 열중량분석기(TGA)를 이용하여 비교 분석하였다.