• Title/Summary/Keyword: Metal Oxide

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Development of multi-cell flows in the three-layered configuration of oxide layer and their influence on the reactor vessel heating

  • Bae, Ji-Won;Chung, Bum-Jin
    • Nuclear Engineering and Technology
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    • v.51 no.4
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    • pp.996-1007
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    • 2019
  • We investigated the influence of the aspect ratio (H/R) of the oxide layer on the reactor vessel heating in three-layer configuration. Based on the analogy between heat and mass transfers, we performed mass transfer experiments to achieve high Rayleigh numbers ranging from $6.70{\times}10^{10}$ to $7.84{\times}10^{12}$. Two-dimensional (2-D) semi-circular apparatuses having the internal heat source were used whose surfaces of top, bottom and side simulate the interfaces of the oxide layer with the light metal layer, the heavy metal layer, and the reactor vessel, respectively. Multi-cell flow pattern was identified when the H/R was reduced to 0.47 or less, which promoted the downward heat transfer from the oxide layer and possibly mitigated the focusing effect at the upper metallic layer. The top boundary condition greatly affected the natural convection of the oxide layer due to the presence of secondary flows underneath the cold light metal layer.

Study on the Improvement of Physicochemical Properties of PEDOT-Metal Oxide Composite Thin Film by Vapor Phase Polymerization (기상중합법으로 제조된 Poly(3,4-ethylenedioxythiophene)(PEDOT)-금속산화물 복합 박막의 물리화학적 물성 향상에 관한 연구)

  • Nam, Mi-Rae;Yim, Jin-Heong
    • Polymer(Korea)
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    • v.36 no.5
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    • pp.599-605
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    • 2012
  • The physicochemical properties such as surface hardness, solvent mechanical wear resistance, and resistance to scratch properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin film prepared by vapor phase polymerization (VPP) was effectively improved by post-treatment of various metal alkoxide sol solutions. Metal oxide layer derived from sol-gel process of metal alkoxide was generated on the PEDOT thin film layer by VPP, resulting in improving mechanical properties of the conductive thin films without any deterioration of their original surface resistance. Several kinds of silicone and titanium alkoxide derivatives with various functional groups were used as metal alkoxide sol sources. Among them, PEDOT-metal oxide composite thin film derived tetraethyl orthosilicate showed the best performance in the terms of surface resistance, transmittance, and various physicochemical properties. The effect of metal alkoxide content in washing solution, oxidant content and drying temperature have been investigated in order to optimize the various properties of PEDOT-metal oxide composite thin film.

Electrical Conductivity Change of Manganese oxide with Addition of Transition Metal (천이금속 첨가에 따른 이산화망간의 전기전도도 변화)

  • Kim, Bong-Seo;Lee, Dong-Yoon;Lee, Hee-Woong;Chung, Won-Sub
    • Proceedings of the KIEE Conference
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    • 2005.07c
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    • pp.2028-2030
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    • 2005
  • The electrical conductivity of manganese oxide and complex manganese oxide produced by anodic deposition method was measured. The additive transition metal is Cu, Co and Fe. The transition metals like as Cu, Co and Fe improved electrical conductivity of complex manganese oxide compared with manganese oxide. This is coincide with the results of molecular orbital calculation by DV-Xa.

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Recent Developments in Metal Oxide Gas Sensors for Breath Analysis (산화물 반도체를 이용한 최신 호기센서 기술 동향)

  • Yoon, Ji-Wook;Lee, Jong-Heun
    • Ceramist
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    • v.22 no.1
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    • pp.70-81
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    • 2019
  • Breath analysis is rapidly evolving as a non-invasive disease recognition and diagnosis method. Metal oxide gas sensors are one of the most ideal platforms for realizing portable, hand-held breath analysis devices in the near future. This paper reviewed the recent developments in metal oxide gas sensors detecting exhaled biomarker gases such as nitric oxides, acetone, ammonia, hydrogen sulfide, and hydrocarbons. Emphasis was placed on strategies to tailor sensing materials/films capable of highly selective and sensitive detection of biomarker gases with negligible cross-response to ethanol, the major interfering breath gas. Specific examples were given to highlight the validity of the strategies, which include optimization of sensing temperature, doping additives, utilizing acid-base interaction, loading catalysts, and controlling gas reforming reaction. In addition, we briefly discussed the design and optimization method of gas sensor arrays for implementing the simultaneous assessment of multiple diseases. Breath analysis using high-performance metal oxide gas sensors/arrays will open new roads for point-of-care diagnosis of diseases such as asthma, diabetes, kidney dysfunction, halitosis, and lung cancer.

Evaluation and Performance Test of Arresters for Electric Power Distribution (전력용 피뢰기의 성능확인시험과 평가 분석)

  • Kim, S.S.;Kim, K.U.;Cho, H.G.;Park, T.G.
    • Proceedings of the KIEE Conference
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    • 1999.07e
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    • pp.2329-2331
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    • 1999
  • Metal oxide surge arrester were developed in the late 1970s, and were immediately adopted as significant breakthrough in over voltage protection of power system. Work was continued throughout the world on the design, development and application of metal oxide surge arrester. This paper describes the evaluating test and results of practical use for analyzing the performance of gapless metal oxide surge arresters under various type test.

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Hydrogen isotope exchange behavior of protonated lithium metal compounds

  • Park, Chan Woo;Kim, Sung-Wook;Sihn, Youngho;Yang, Hee-Man;Kim, Ilgook;Lee, Kwang Se;Roh, Changhyun;Yoon, In-Ho
    • Nuclear Engineering and Technology
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    • v.53 no.8
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    • pp.2570-2575
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    • 2021
  • The exchange behaviors of hydrogen isotopes between protonated lithium metal compounds and deuterated water or tritiated water were investigated. The various protonated lithium metal compounds were prepared by acid treatment of lithium metal compounds with different crystal structures and metal compositions. The protonated lithium metal compounds could more effectively reduce the deuterium concentration in water compared with the corresponding pristine lithium metal compounds. The H+ in the protonated lithium metal compounds was speculated to be more readily exchangeable with hydrons in the aqueous solution compared with Li+ in the pristine lithium metal compounds, and the exchanged heavier isotopes were speculated to be more stably retained in the crystal structure compared with the light protons. When the tritiated water (157.7 kBq/kg) was reacted with the protonated lithium metal compounds, the protonated lithium manganese nickel cobalt oxide was found to adsorb and retain twice as much tritium (163.9 Bq/g) as the protonated lithium manganese oxide (69.9 Bq/g) and the protonated lithium cobalt oxide (75.1 Bq/g) in the equilibrium state.

Synthesis and Compaction of Al-based Nanopowders by Pulsed Discharge Method

  • Rhee, Chang-Kyu;Lee, Geun-Hee;Kim, Whung-Whoe
    • Journal of Powder Materials
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    • v.9 no.6
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    • pp.433-440
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    • 2002
  • Synthesis and compaction of Al-base nano powders by pulsed discharge method were investigated. The aluminum based powders with 50 to 200 nm of diameter were produced by pulsed wire evaporation method. The powders were covered with very thin oxide layer. The perspective process for the compaction and sintering of nanostructured metal-based materials stable in a wide temperature range can be seen in the densification of nano-sized metal powders with uniformly distributed hard ceramic particles. The promising approach lies in utilization of natural uniform mixtures of metal and ceramic phases, e.g. partially oxidized metal powders as fabricated in our synthesis method. Their particles consist of metal grains coated with oxide films. To construct a metal-matrix material from such powder, it is necessary to destroy the hard oxide coatings of particles during the compaction process. This goal was realized in our experiments with intensive magnetic pulsed compaction of aluminum nanopowders passivated in air.

Size, Shape, and Crystal Structure-dependent Toxicity of Major Metal Oxide Particles Generated as Byproducts in Semiconductor Fabrication Facility (반도체 가공 작업환경에서 부산물로 발생되는 주요 금속산화물의 입자 크기, 형상, 결정구조에 따른 독성 고찰)

  • Choi, Kwang-Min
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.26 no.2
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    • pp.119-138
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    • 2016
  • Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

Two dimensional tin sulfide for photoelectric device

  • Patel, Malkeshkumar;Kim, Joondong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.389.1-389.1
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    • 2016
  • The flexible solid state device has been widely studied as portable and wearable device applications such as display, sensor and curved circuits. A zero-bias operation without any external power consumption is a highly-demanding feature of semiconductor devices, including optical communication, environment monitoring and digital imaging applications. Moreover, the flexibility of device would give the degree of freedom of transparent electronics. Functional and transparent abrupt p/n junction device has been realized by combining of p-type NiO and n-type ZnO metal oxide semiconductors. The use of a plastic polyethylene terephthalate (PET) film substrate spontaneously allows the flexible feature of the devices. The functional design of p-NiO/n-ZnO metal oxide device provides a high rectifying ratio of 189 to ensure the quality junction quality. This all transparent metal oxide device can be operated without external power supply. The flexible p-NiO/n-ZnO device exhibit substantial photodetection performances of quick response time of $68{\mu}s$. We may suggest an efficient design scheme of flexible and functional metal oxide-based transparent electronics.

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Synthesis of Metal Oxide Semiconductor Nanostructures and Their Gas Sensing Properties (금속 산화물 반도체 나노구조의 합성과 가스 감응 특성)

  • Choi, Kwon-Il;Lee, Jong-Heun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.8
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    • pp.632-638
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    • 2012
  • The prepartion of various metal oxide nanostructures via hydrothermal method, hydrolysis, thermal evaporation and electrospinning and their applications to chemoresistive sensors have been investigated. Hierarchical and hollow nanostructures prepared by hydrothermal method and hydrolysis showed the high response and fast responding kinetics on account of their high gas accessibility. Thermal evaporation and electrospinning provide the facile routes to prepare catalyst-loaded oxide nanowires and nanofibers, respectively. The loading of noble metal and metal oxide catalyst were effective to achieve rapid response/recovery and selective gas detection.