• Title, Summary, Keyword: Multipod

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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.

Effect of Temperature Gradient on the Characteristics of GaN Nanorods Grown on R-plane Sapphire Substrates (기판 주변 반응 기체와 기판 사이의 온도 차이에 따른 r-면 사파이어 기판에 성장된 길화갈륨 나노 막대의 특성 변화 연구)

  • Shin, Bo-A;Kim, Chin-Kyo
    • Journal of the Korean Vacuum Society
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    • v.18 no.1
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    • pp.44-48
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    • 2009
  • The effect of temperature gradient between the substrate and ambient gas on the structural characteristics of GaN nanorods grown on r-plane sapphire substrates by hydride vapor phase epitaxy was investigated. The density, diameter, and length strongly depended on the tempearture gradient. In addition, the cross-sectional shape of the nanorrods at the end of growth was found to be more dependedent on the temperature of a substrate itself than the temperature gradient.

A Study on the Suitability of Suction Caisson Foundation for the 5Mw Offshore Wind Turbine (5MW급 해상풍력발전시스템용 Suction Caisson 하부구조물 적합성 연구)

  • Kim, Yong-Chun;Chung, Chin-Wha;Park, Hyun-Chul;Lee, Seunug-Min;Kwon, Dae-Yong;Shi, Wei
    • New & Renewable Energy
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    • v.6 no.3
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    • pp.47-54
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    • 2010
  • Foundation plays an important role in the offshore wind turbine system. Different from conventional foundations, the suction caisson is proven to be economical and reliable. In this work, three-dimensional finite element method is used to check the suitability of suction caisson foundation. NREL 5MW wind turbine is chosen as a baseline model in our simulation. The maximum overturning moment and vertical load at the mudline are calculated using FAST and Bladed. Meanwhile the soil-structure interaction response from our simulation is also compared with the experiment data from Oxford university. The design parameter such as caisson length, diameter of skirt and spacing of multipod are investigated. Accordingly based on these parameters suggestions are given to use suction caisson foundations more efficiently.

Synthesis of zinc oxide nanoparticles via aqueous solution routes (수용액 합성법에 의한 ZnO 나노분말의 합성)

  • Koo, Jin Heui;Yang, Jun Seok;Cho, Soo Jin;Lee, Byeong Woo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.26 no.5
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    • pp.175-180
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    • 2016
  • ZnO nanoparticles were synthesized by aqueous preparation routes of a precipitation and a hydrothermal process. In the processes, the powders were formed by mixing aqueous solutions of Zn-nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) with NaOH aqueous solution under controlled reaction conditions such as Zn precursor concentration, reaction pH and temperature. Single ZnO phase has been obtained under low Zn precursor concentration, high reaction pH and high temperature. The synthesized particles exhibited flakes (plates), multipods or rods morphologies and the crystallite sizes and shapes would be efficiently controllable by changing the processing parameters. The hydrothermal method showed advantageous features over the precipitation process, allowing the precipitates of single ZnO phase with higher crystallinity at relatively low temperatures below $100^{\circ}C$ under a wider pH range for the Zn precursor concentration of 0.1~1 M.