• Title/Summary/Keyword: Dispersive material

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Microstructure Property of High Voyage Motor Stator Insulation (고압전동기 고정자 권선 절연재료의 미세구조 특성)

  • 김희동;주영호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.05a
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    • pp.513-517
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    • 1999
  • High voltage motor(rated 6.6kV and 448kw) has failed in the stator endwinding area during normal service. Experiments on microstructure property were conducted using the control and aged insulations, which were drawn out from stator windings of the high voltage motor. The analyses were characterized using stereozoom microscope(SM), scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy(EDS). SM result shows that large voids are present in the interface between turn insulation and groundwall insulation. SEM results indicated that the groundwall insulation is rarely thermal stress. EDS results showed that chemical elements in the high voltage motor stator insulations were Al, Si, O, K and Fe.

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A Study on Structural and Dielectric Properties of the (Ba,Sr)TiO$_3$ Thin Films Prepared by Laser Ablation (레이저 어블레이션법으로 제작될 (Ba, Sr)TiO$_3$ 박막의 구조 및 유전특성에 관한 연구)

  • 주학림;김성구;장낙원;마석범;백동수
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.05a
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    • pp.122-125
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    • 1999
  • (Ba$_{0.6}$Sr$_{0.4}$)TiO$_3$(BST) thin films were fabricated with different deposition temperature and oxygen pressure by Pulsed Laser Deposition(PLD). Energy Dispersive Spectroscopy(EDS) proved that BST thin films prepared by PLD have almost the same stoichiometric composition as the BST target materials. This BST thin films were fully crystallized at $650^{\circ}C$, 300mTorr oxygen pressure and showed a maximum dielectric constant value of $\varepsilon$$_{t}$=684 and dielectric loss was 0.01 at 75$0^{\circ}C$, 300mTorr oxygen pressure.ssure.

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Fabrication of ZnO Nanowires by Direct Melt Oxidation of Al-Zn Alloy (Al-Zn 합금의 직접용융산화법을 이용한 ZnO 나노와이어의 제작)

  • Lee, Geun-Hyoung;Kim, Il-Soo;Shin, Byoung-Chul;Lee, Won-Jae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.11
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    • pp.995-999
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    • 2008
  • ZnO nanowires with tetrapod shape were formed on the surface of the sample by direct melt oxidation of Al-Zn alloy at $1000^{\circ}C$ in air. X-ray diffraction (XRD) pattern revealed that the ZnO nanowires had wurtzite structure of hexagonal phase. Any other element except Zn and O was not detected in energy dispersive X-ray spectrum. The c- and a-axis lattice constants estimated from the XRD pattern were 0.520 and 0.325 nm, respectively. These are in well accordance with those of bulk ZnO single crystal, indicating high quality crystallinity. The green light emission at a wavelength of 510 nm was observed from the nanowires at room temperature, which was ascribed to high density of oxygen vacancies in nanowires.

Determination of Thin Film Thickness by EDS Analysis and its Modeling (EDS 분석과 모델링에 의한 박막두께 측정 방법에 관한 연구)

  • Yun, Jae-Jin;Lee, Won-Jong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.8
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    • pp.647-653
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    • 2011
  • In this study, a method to measure the thickness of thin film by EDS (energy dispersive spectroscopy) is suggested. We have developed a model which calculates the thickness of thin film from the characteristic x-ray intensity ratio of the elements in thin film and substrate by considering incident electron beam energy, x-ray generation curve, backscattering and absorption of x-ray, take-off angle of x-ray and tilt angle of the sample. We obtained the relation curve between the film thickness measured experimentally and the x-ray intensity ratio of elements. The film thicknesses calculated from the model agrees quite well with those measured experimentally. Therefore, the thin film thickness can be measured rapidly and accurately by using the model developed in this study and the x-ray intensity ratio obtained in EDS analysis.

Synthesis and Cathodoluminescence of Tetrapod and Multipod-shaped ZnO Nanostructures by Oxidation of Zn in Air Atmosphere (공기 중 대기압 분위기에서 Zn의 산화에 의해 생성된 Tetrapod와 Multipod 형태의 나노구조와 음극선 발광 특성)

  • Lee, Geun-Hyoung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.3
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    • pp.256-260
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    • 2011
  • ZnO nanostructures with tetrapod, needle and multipod shapes were synthesized without catalysts through a simple thermal oxidation of metallic Zn powder in alumina crucible under air atmosphere. X-ray diffraction data revealed that the ZnO nanostructures had wurtzite structure of hexagonal phase. Energy dispersive X-ray (EDX) spectra showed that the ZnO was of high purity. After the oxidation of Zn powder, white colored product was mainly observed and yellow colored product was observed only a very little on the surface of the oxidized source materials. The white product consisted of tetrapods, while yellow product was composed of needles and multipods. Cathodoluminescece spectra showed that the crystalline quality of tetrapods was better that those of needles and multipods.

A Study on the Atomic and Electronic Structures of DNA-nucleobases-adsorbed Graphene Through First-principles LCAO Method (제일원리 LCAO 방법을 이용한 DNA Nucleobase 흡착된 그라핀의 원자 및 전자구조 연구)

  • Lee, Eun-Cheol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.6
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    • pp.510-514
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    • 2011
  • Based on first-principles LCAO method, we study the electronic and atomic structures of DNA nucleobases adenine (A), thymine (T), guanine (G), and cytosine (C) adsorbed on graphene surfaces. The ${\pi}-{\pi}$ stacking interactions between graphene and nucleobases lead to the bilayer geometries similar to the Bernal stacked graphite. Through the density of states and charge density analyses, it is found that nucleobases are physisorbed on graphene by dispersive interactions with negligible charge exchange. Our calculations reproduce the atomic structures obtained in previous plane wave calculations accurately with much less computation, and well describe the delocalized ${\pi}-{\pi}$ interactions in graphene-nucleobases system, indicating that the LCAO method is very efficient for investigating graphene-bio systems.

Afterglow Effect from Adding BaF2 to Oxyfluoride Glass Ceramic Containing Eu2+-doped Nepheline

  • Lee, Hansol;Chung, Woon Jin
    • Current Optics and Photonics
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    • v.6 no.4
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    • pp.413-419
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    • 2022
  • An oxyfluoride glass ceramic containing Eu2+-doped nepheline and LaF3 crystals was modified, with BaF2 replacing LaF3 up to 20 mole percent, and its luminescence change was monitored. With increasing BaF2 content, the greenish yellow emission centered at 540 nm under 400-nm excitation decreased, and a new afterglow emission from the modified ceramic was observed after removal of the excitation light source. X-ray diffraction (XRD) and transmission electron microscopy with energy dispersive spectroscopy (TEM-EDS) were used to investigate the changes in the crystalline phases within the glass matrix. Time dependent emission intensity was monitored to observe the afterglow, and the possible mechanism for the afterglow due to BaF2 addition was considered.

A facile chemical synthesis of a novel photo catalyst: SWCNT/titania nanocomposite

  • Paul, Rima;Kumbhakar, Pathik;Mitra, Apurba K.
    • Advances in nano research
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    • v.1 no.2
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    • pp.71-82
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    • 2013
  • A simple chemical precipitation technique is reported for the synthesis of a hybrid nanostructure of single-wall carbon nanotubes (SWCNT) and titania ($TiO_2$) nanocrystals of average size 5 nm, which may be useful as a prominent photocatalytic material with improved functionality. The synthesized hybrid structure has been characterized by transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDAX), powder X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It is clearly revealed that nearly monodispersed titania nanocrystals (anatase phase) of average size 5 nm decorate the surfaces of SWCNT bundles. The UV-vis absorption study shows a blue shift of 16 nm in the absorbance peak position of the composite material compared to the unmodified SWCNTs. The photoluminescence study shows a violet-blue emission in the range of 325-500 nm with a peak emission at 400 nm. The low temperature electrical transport property of the synthesized nanomaterial has been studied between 77-300 K. The DC conductivity shows semiconductor-like characteristics with conductivity increasing sharply with temperature in the range of 175-300 K. Such nanocomposites may find wide applications as improved photocatalyst due to transfer of photo-ejected electrons from $TiO_2$ to SWCNT, thus reducing recombination, with the SWCNT scaffold providing a firm and better positioning of the catalytic material.

Evaluation of Environment Imapcts on TiN-ZrCo Composites Hydrogen Seperation by Material Life Cycle Assessment (TiN-ZrCo 복합수소 분리막의 제조와 환경성 평가)

  • KIM, MINGYEOM;AHN, JOONGWOO;HONG, TAEWHAN
    • Transactions of the Korean hydrogen and new energy society
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    • v.28 no.6
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    • pp.627-634
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    • 2017
  • In this study, Material life cycle evaluation was performed to analyze the environmental impact characteristics of TiN-ZrCo membrane manufacturting process. Gabi was used as software. The Eco-Indicator 99 methodology was used to evaluate the 11 impact categories and the 10 impact categories using the CML 2001 methodology. Precursor TiN was synthesized by sol-gel method and zirconium was coated by ball mill method. The metallurgical, physical and thermodynamic characteristics of the membranes were analyzed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDS), X-ray Diffraction (XRD), Thermo Gravimetry/Differential Thermal Analysis (TG/DTA), Brunauer, Emmett, Teller (BET) and Gas Chromatograph System (GP). As a result of the characterization and normalization, the environmental impacts of each category of impacts were GWP 100 years with the highest environmental impact of 99.9%.

Effects of Counterpart Materials on Wear Behavior of Thermally Sprayed STS316 Coatings (STS316 용사코팅층의 마모거동에 미치는 상대마모재의 영향)

  • Lee, Jae-Hong;Kim, Yeong-Sik
    • Journal of Power System Engineering
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    • v.18 no.6
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    • pp.58-63
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    • 2014
  • This paper deals with the effects of counterpart materials on the wear behavior of thermally sprayed STS316 coatings. STS316 powders were flame-sprayed onto a carbon steel substrate. Dry sliding wear tests were performed using the applied loads of 15 N. AISI52100, $Al_2O_3$, $ZrO_2$ and $Si_3N_4$ balls were used as counterpart materials. Wear behavior of STS316 coatings against different counterpart materials were studied using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDS). The results show that the wear behavior of thermally sprayed STS316 coatings strongly depends on the type of counterpart material. Dominant wear mechanism was similar for all studied materials as failure of adhesion film except for Si3N4 used as counterpart material. In the case of Si3N4 used as counterpart material, dominant wear mechanism was abrasion.