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Synthesis of AlO(OH) Nano Colloids from γ-Al2O3 via Reversible Process (γ-Al2O3로부터 가역과정을 경유한 AlO(OH) 나노콜로이드의 합성)

  • Cho, Hyun-Ran;Kim, Sook-Hyun;Park, Byung-Ki
    • Journal of the Korean Ceramic Society
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    • v.46 no.3
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    • pp.288-294
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    • 2009
  • The platelet AlO(OH) nano colloids were prepared by hydrothermal reaction of the $\gamma-Al_2O_3$ obtained with dehydration of $\gamma$-AlO(OH) and dilute $CH_3COOH$ solution. In hydrothermal reaction process, reversible reaction was accompanied between $\gamma-Al_2O_3$ and AlO(OH), and hydrothermal reaction temperature, hydrothermal reaction time and $CH_3COOH$ concentration had an effect on the crystal structure, surface chemical property, surface area, pore characteristics and crystal morphology of the AlO(OH) nano colloid particles. In this study, it was investigated to the hydrothermal reaction condition of the AlO(OH) nano colloid for using catalyst support, heat resisting agent, adsorbents, binder, polishing agent and coating agent. The crystal structure, surface area, pore volume and pore size of the platelet AlO(OH) nano colloids were investigated by XRD, TEM, TG/DTA, FT-IR and $N_2$ BET method in liquid nitrogen temperature.

Binary Metal Oxide ($IrO_2-RuO_2$) pH Sensor Prepared by Sol-gel Method (Sol-gel 법을 이용한 이성분 금속산화물 ($IrO_2-RuO_2$) pH 센서)

  • Lee, Jeong-Ran;Oh, Se-Lim;Han, Won-Sik;Hong, Tae-Kee
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.2
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    • pp.190-196
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    • 2014
  • The sol-gel method was used to prepare binary metal oxide ($IrO_2-RuO_2$) pH sensor. The electrodes that mole percent compositions (mol%) of $IrO_2$ and RuO2 were 70:30 and 30:70 were selected. The characterizations of Nernstian response over pH range, response rate, interference on alkaline metals and reproducibility were investigated. Also the electroanalytical properties of these electrodes were evaluated in comparison with a commercial glass pH electrode. The composition of $IrO_2:RuO_2$ 70:30 mol% was chosen as better electrode formulation. The electrode was not susceptible to the action of interfering ions such as $Li^+$, $Na^+$ and $K^+$.

Oxidation Resistance and Electrical Conductivity of $Ti_3SiC_2$ with Thin Oxide Layer

  • Hwang, Sung-Ik;Han, Kyoung-Ran;Kim, Chang-Sam
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1110-1111
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    • 2006
  • [ $Ti_3SiC_2$ ] was coated with $Al_2O_3$, MgO and $SiO_2$ respectively by sol-gel method and cured at 900 and $1200^{\circ}C$. The coated oxides did not react with $Ti_3SiC_2$ at $900^{\circ}C$ but reacted with it to form $TiC_x$ at $1200^{\circ}C$. The specimen coated with $SiO_2$ at $900^{\circ}C$ formed a dense protecting layer and showed the best oxidation resistance at $800^{\circ}C$ in air. However, the dense protecting layers did not form in $Al_2O_3$ and MgO coated specimens cured even at $900^{\circ}C$. MgO coated specimen showed the worst improvement in the oxidation resistance because the reactivity of MgO with $Ti_3SiC_2$ was highest. On the other hand, the electrical conductivities were measured in MgO and $Al_2O_3$ coated specimens to have TiCx but could not be measured in the $SiO_2$ coated ones because of the nonconductive dense protected layers.

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Study on nuclear magnetic resonance of superionic conductor NH4HSeO4 in rotating frame

  • Choi, Jae Hun;Lim, Ae Ran
    • Journal of the Korean Magnetic Resonance Society
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    • v.18 no.1
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    • pp.41-46
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    • 2014
  • In order to obtain information on the structural geometry of $NH_4HSeO_4$ near the phase transition temperature, the spectrum and spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for the ammonium and hydrogen-bond protons were investigated through $^1H$ MAS NMR. $T_{1{\rho}}$ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in $O-H{\cdots}O$ bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.

The crystallization characteristic of ZnO films deposition at low temperature by oxygen flow rate and RF power (저온공정에서 RF 파워와 산소유량에 의한 ZnO 박막의 결정성 연구)

  • Wen, Long;Kim, Hye-Ran;Jin, Su-Bong;Choe, Yun-Seok;Choe, In-Sik;Han, Jeon-Geon
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2012.05a
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    • pp.343-345
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    • 2012
  • 대향 타겟 스퍼터링법 (Facing Targets Sputtering)을 이용하여 저온 공정에서 ZnO 박막을 증착하였다. 이 실험에서 두 개의 타겟의 거리를 110nm로 고정하고 박막의 증착두께를 150nm로 정하였다. 산소 가스의 유량, 인가 전력을 변수로 하였을 경우 ZnO 박막의 방향성과 결정성을 XRD로 측정하고 분석하였다. 그 결과 인가전압과 산소 유량의 증가에 따라 결정성은 좋아진다.

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