• 제목/요약/키워드: nano crystalline

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Phase stability and Morphology of high-k gate stack of $Si/SiO_2/HfO_2$ and $Si/SiO_2/ZrO_2$

  • Lee, Seung-Hwan;Bobade, Santosh M.;Yoo, W.J.
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2007년도 추계학술대회 논문집
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    • pp.118-119
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    • 2007
  • Phase stability and morphological investigation on the $Si/SiO_2/HfO_2$ and $Si/SiO_2/ZrO_2$ stack are presented. Thermal stability of $HfO_2$ and $ZrO_2$ determines the quality of interface and subsequently the performance of device. The stacks have been fabricated and annealed at $1000^{\circ}C$ for various time. In evolution of crystalline phase and morphology (electrical and geometrical) of high-k materials, annealing time and process are observed to be crucial factors. The crystallization of some phase has been observed in the case of $Si/SiO_2/HfO_2$. The chemical environment around Zr and Hf in respective samples is observed to be different.

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나노구조 TiO$_2$ 용사코팅의 미세조직 제어 공정기술 개발과 광촉매 특성평가 - Part I: TiO$_2$코팅 - (Photocatalytic Property of Nano-Structured TiO$_2$ Thermal Splayed Coating - Part I: TiO$_2$ Coating -)

  • 이창훈;최한신;이창희;김형준;신동우
    • Journal of Welding and Joining
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    • 제21권4호
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    • pp.39-45
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    • 2003
  • Nano-TiO$_2$ photocatalytic coatings were deposited on the stainless steel 304(50$\times$70$\times$3mm) by the APS(Atmospheric Plasma Spraying). Photocatlytic reaction was tested in MB(methylene blue) aqueous solution. For applying nano-TiO$_2$ powders by thermal spray, the starting nano-TiO$_2$ powder with 100% anatase crystalline was agglomerated by spray drying. Plasma second gas(H$_2$) flow rate and spraying distance were used as principal process parameters which are known to control heat enthalpy(heat input). The relationship between process parameters and the characteristics of microstructure such as the anatase phase fraction and grain size of the TiO$_2$ coatings were investigated. The photo-decomposition efficiency of TiO$_2$ coatings was evaluated by the kinetics of MB aqueous solution decomposition. It was found that the TiO$_2$ coating with a lower heat input condition had a higher anatase fraction, smaller anatase grain size and a better photo-decomposition efficiency.

알루미늄 나노 분말의 수화반응에 의한 수산화알루미늄 형성 (Formation of an Aluminum Hydroxide Fiber by a Hydrolysis of Aluminum Nano Powder)

  • 이근희;오영화;이창규;김흥회
    • 한국재료학회지
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    • 제15권3호
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    • pp.172-176
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    • 2005
  • Formation of aluminum hydroxide by a hydrolytic reaction of nano aluminum powder synthesized by a pulsed wire evaporation (PWE) method has been studied. The type and morphology of the hydroxides were investigated with various initial temperatures and pHs. The nano fibrous boehmite (AlOOH) was formed predominantly over $40^{\circ}C$ of the hydrolytic temperature in acid solution, while the bayerite $(Al(OH)_3)$ was formed predominantly below $30^{\circ}C$ in alkali solution with a faceted crystalline structure. As a result the boehmite showed a much larger specific surface area (SSA) than that of bayerite. The highest SSA of the boehmite was about $409\;m^2/g$.

결정질 실리콘 태양전지의 Ag 촉매층을 이용한 나노 텍스쳐링 공정에 관한 연구 (The Study of Nano-texturing Process for Crystalline Silicon Solar Cell Using Ag Catalyst Layer)

  • 오병진;여인환;김민영;임동건
    • 한국전기전자재료학회논문지
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    • 제25권1호
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    • pp.58-61
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    • 2012
  • In our report a relatively simple process for fast nano-texturing of p-type(100) CZ- silicon surface using silver catalyzed wet chemical etching in aqueous hydrofluoric acid (HF) and hydrogen peroxide solution($H_2O_2$) at room temperature. The wafers were saw-damaged by NaOH(6 wt%) at $60^{\circ}C$ for 150s. To obtain a nano-structured black surface, a thin layer of silver with thickness of 1 - 10 nm was deposited on the surfaces by evaporation system. After this process the samples were etched in HF : $H_2O_2$ : $H_2O$ = 1:5:10 at room temperature for 80s - 220s. Due to the local catalytic of the Ag clusters, this treatment results in the nano-scale texturing on the surface. This resulted in average reflectance values less than 9% after the silver on the surface of the wafers were removed.

Fe계 나노결정립 분말의 표면 산화에 따른 전자파 흡수특성 (Effect of the Surface Oxidation on the Electromagnetic Wave Absorption Behavior of a Fe-based Nanocrystalline Alloy)

  • 구숙경;우수정;문병기;송용설;박원욱;손근용
    • 한국분말재료학회지
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    • 제14권5호
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    • pp.303-308
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    • 2007
  • The oxidation of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder has been conducted to investigate its influence on the electromagnetic wave absorption characteristics of the soft magnetic material. Oxidation occurred primarily on the surface of nanocrystals. Oxidation reduced the real part of complex permeability due to the reduction of the relative volume of the powder, which otherwise contributes to the permeability. Oxidation reduced the absorption efficiency of the sheet at frequencies over 1GHz, indicating that the relative contribution of skin depth increments to the absorption was not significant. The pulverization and milling process lowered the optimum crystallization temperature of the material by $40{\sim}50^{\circ}C$ because of the internal energy accumulated during the fragmentation and powder thinning processes.

Synthesis and Characterization of ZnxMN1−xFe2O4 Nanoparticles by a Reverse Micelle Process

  • Kim, Sun-Woog;Kim, Hyeon-Cheol;Kim, Jun-Seop;Kim, Hyun-Ju;Bae, Dong-Sik
    • 한국세라믹학회지
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    • 제45권6호
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    • pp.320-323
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    • 2008
  • The preparation of $Zn_xMn_{1-x}Fe_2O_4$ nanoparticles in an Igepal CO-520-cyclohexane water reverse micelle solution has been studied. The transmission electron microscopy and X-ray diffraction pattern analyses revealed the resulting particles to be $Zn_xMn_{1-x}Fe_2O_4$. The average size and distribution of the synthesized particles calcined at $500^{\circ}C$ for 5 h were in the range of 10 to 20 nm and broad, respectively. The phase of the synthesized particles was crystalline, the magnetic behavior of the synthesized particles was ferromagnetic. The effect of the synthesis parameters, such as the molar ratio of water to surfactant and calcination temperature, is discussed.

Synthesis and Characterization of NixMn1-xFe2O4 Nanoparticles by a Reverse Micelle Process

  • Kim, Sun-Woog;Kim, Hyeon-Cheol;Kim, Jun-Seop;Kim, Hyun-Ju;Bae, Dong-Sik
    • 한국재료학회지
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    • 제18권6호
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    • pp.298-301
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    • 2008
  • A preparation of $Ni_xMn_{1-x}Fe_2O_4$ nanoparticles produced via the reduction of Nickel nitrate hexahydrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate with hydrazine in Igepal CO-520/cyclohexane reverse micelle solutions was investigated. Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and Vibration Sample Magnetometer (VSM) analyses showed that the resultant nanoparticles increased the molar ration of water to Igepal CO-520 as the concentrations of Nickel nitrate hexahyrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate increased. The average size of the synthesized particles calcined at $600^{\circ}C$ for 2hrs was in the range of 20 nm to 30 nm, and the particle distribution was broadened. The phase of the synthesized particles was crystalline, and the magnetic behavior of the synthesized particles was superparamagnetism. The effect of the synthesis parameters of the molar ratio of water to surfactant and the calcination temperature was discussed.

Cold Compaction Behavior of Nano and Micro Aluminum Powder under High Pressure

  • Kim, Dasom;Park, Kwangjae;Kim, Kyungju;Cho, Seungchan;Hirayama, Yusuke;Takagi, Kenta;Kwon, Hansang
    • Composites Research
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    • 제32권3호
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    • pp.141-147
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    • 2019
  • In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

양극산화법에 의한 니오븀 산화물 나노로드 제조 (Fabrication of Niobium Oxide Nanorods by the Anodization Method)

  • 정은혜;장정호;정봉용
    • 전기화학회지
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    • 제14권4호
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    • pp.196-200
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    • 2011
  • 본 연구에서는 니오븀 산화물을 비교적 저온에서 단시간 동안의 양극산화법을 통해 제조하였다. 이때, 전해질로는 NaF와 HF를 혼합하여 사용하였으며, 20~120 V의 다양한 전압 조건에 따라 생성되는 니오븀 산화물의 미세구조를 관찰하였다. 일반적으로 니오븀 금속의 양극산화 시 초기에 생성된 니오븀 산화물은 무정형 구조이나 반응이 경과함에 따라 점차 결정형 산화물로 성장하게 된다. 이러한 산화물은 XRD 분석을 통하여 결정형의 $Nb_2O_5$ 임을 확인하였고, FE-SEM 분석결과, 그 표면은 매우 밀집된 형태의 나노로드로 이루어진 마이크로콘 산화물임을 알 수 있었다. 적절한 공정변수로 제조된 니오븀 산화물은 마이크로콘 구조 전체 표면에 걸쳐 동일한 크기를 갖는 나노로드 다발을 형성하고 있으며, 이러한 나노 구조는 또한 넓은 표면적을 기대할 수 있어 염료감응 태양전지나 바이오 소재 등에 대한 다양한 분야에 응용될 수 있을 것으로 기대된다.