• Title/Summary/Keyword: oxygen effect

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Effect of Oxygen on the Microstructure and Mechanical Properties of Cr-O-N Coatings (Oxygen 함량에 따른 Cr-O-N 코팅막의 미세구조 및 기계적 특성에 관한 연구)

  • Yun, Jun-Seo;Kwon, Se-Hun;Park, In-Wook;Lee, Jeong-Du;Kim, Kwang-Ho
    • Journal of Surface Science and Engineering
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    • v.42 no.5
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    • pp.220-226
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    • 2009
  • Cr-O-N coatings having different oxygen contents were deposited on Si wafer and SUS 304 substrates by an arc ion plating technique using Cr target in $Ar/O_2/N_2$ gaseous atmosphere. As increasing oxygen content in the coating, the microstructure of Cr-O-N coating changed from polycrystalline having NaCl structure to amorphous structure. Further increase of oxygen content resulted in phase transformation from amorphous to rhombohedral structure. From the variations of d value and average grain size, it was revealed that the maximum solubility of oxygen in Cr-O-N coating was about 21 at.%. And the maximum micro-hardness of 2751HK was obtained in this composition. The lowest friction coefficient was measured in the coating having 34.8 at.% of oxygen. However, more narrow width of wear track was found in the coating having 30.1 at.% of oxygen.

Effect of Acvated Oxygen Plasma on the Crystallinity and Superconductivity of $Yba_2Cu_3-O_{7-x}$ Thin Films Prepated by Reactive Co-evaporation method

  • Chang, Ho-Jung;Kim, Byoung-Chul;Akihama, Ryozo;Song, Jin-Tae
    • Korean Journal of Materials Research
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    • v.4 no.3
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    • pp.280-286
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    • 1994
  • As-grown $YBa_2Cu_3O_{7-x}$ films on MgO(100)substrates were prepated by a reactive co-evaporation method, and effects of activated oxygen plasma on the crystallinity and superconductivity at substrate temperature ranging from $450^{\circ}C$ to $590^{\circ}C$ were investigated. The film deposited under the activated oxygen plasma at the substrate temperature of $590^{\circ}C$ had a single crystal phase. Whereas, when films were deposited under only oxygen gas, they were not in perfect single crystal phase but with slight polycrystalline nature. When the substrate temperature was $590^{\circ}C$, $Tc_{zero}$'s were 83K and 80K for films with and without activated oxygen plasma, respectively. The critical temperature, the crystal structure and the surface morphology of as-grown films were found to be insensitive to the activated oxygen plasma which is introduced during deposition instead of oxygen gas, but the crystalline quality was improved somewhat by the introduction by the introduction of actvated oxygen plasma.

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Fundamental Mechanisms of Platinum Catalyst for Oxygen Reduction Reaction in Fuel Cell: Density Functional Theory Approach (연료전지 산소환원반응 향상 위한 백금 촉매의 구조적 특성: 밀도범함수이론 연구)

  • Kang, Seok Ho;Lee, Chang-Mi;Lim, Dong-Hee
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.5
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    • pp.242-248
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    • 2016
  • The overall reaction rate of fuel cell is governed by oxygen reduction reaction (ORR) in the cathode due to its slowest reaction compared to the oxidation of hydrogen in the anode. The ORR efficiency can be readily evaluated by examining the adsorption strength of atomic oxygen on the surface of catalysts (i.e., known as a descriptor) and the adsorption energy can be controlled by transforming the surface geometry of catalysts. In the current study, the effect of the surface geometry of catalysts (i.e., strain effect) on the adsorption strength of atomic oxygen on platinum catalysts was analyzed by using density functional theory (DFT). The optimized lattice constant of Pt ($3.977{\AA}$) was increased and decreased by 1% to apply tensile and compressive strain to the Pt surface. Then the oxygen adsorption strengths on the modified Pt surfaces were compared and the electron charge density of the O-adsorbed Pt surfaces was analyzed. As the interatomic distance increased, the oxygen adsorption strength became stronger and the d-band center of the Pt surface atoms was shifted toward the Fermi level, implying that anti-bonding orbitals were shifted to the conduction band from the valence band (i.e., the anti-bonding between O and Pt was less likely formed). Consequently, enhanced ORR efficiency may be expected if the surface Pt-Pt distance can be reduced by approximately 2~4% compared to the pure Pt owing to the moderately controlled oxygen binding strength for improved ORR.

An Experimental Study on the Efficacy of Vitamin E aganinst Oxygen Toxicity (산소중독에 대한 Vitamin E의 보호효과에 관한 실험적 연구)

  • Lee, Sung-Gyu;Lee, Sang-Il;Cho, Soo-Hun;Yun, Dork-Ro
    • Journal of Preventive Medicine and Public Health
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    • v.19 no.2 s.20
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    • pp.184-192
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    • 1986
  • Since the wide spread application of hyperbaric oxygenation in clinical setting, the problems of oxygen toxicity have been attracting a deep interest from the researchers on hyperbaric medicine as a practical issue. Among extensive research trials, the study on the protective agents against oxygen toxicity occupied one of the most challenging field. As the mechanisms of oxygen toxicity, the role of the oxygen free radicals produced by peroxidation process are strongly accepted by the leading researchers on oxygen toxicity, the probable protective effects of antioxidant against oxygen toxicity are sustaining a sufficient rationale. In this study, the author attempted to evaluate the effect of vitamin E as a protective agent against oxygen toxicity through the observation of death rate, convulsion rate, time to convulsion, and macroscopic and microscopic pathological changes of experimental rats exposed to 100% oxygen at 5 ATA for 120 minutes. The findings observed are as follows: 1) The death rate, convulsion rate, time to convulsion, organ/body weight ratio and microscopic pathological findings were identified as reliable objective and quantitative indices for oxygen toxicity. 2) Vitamin E showed excellent protective effects against CNS and pulmonary oxygen toxicity as a strong antioxidant. The most effective dose seemed to be around 400 mg/kg 3) The results of this study are supporting the oxygen free radical hypothesis on oxygen toxicity.

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The Effect of Oxygen in Low Temperature SCR over Mn/$TiO_2$ Catalyst (Mn/$TiO_2$ 촉매를 이용한 저온 SCR 반응에서 산소의 영향)

  • Lee, Sang Moon;Choi, Hyun Jin;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.23 no.1
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    • pp.119-123
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    • 2012
  • This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

Effect of Cobalt Oxide on Carbothermal Reduction of Spray Dried Titanium-Cobalt-Oxygen Based Oxide Powder (분무건조법에 의해 제조된 Ti-Co-O계 산화물 분말의 환원/침탄반응에 미치는 코발트 산화물의 영향)

  • Lee, Gil-Geun;Kim, Chan-Young
    • Journal of Powder Materials
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    • v.12 no.5 s.52
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    • pp.336-344
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    • 2005
  • In the present study, the focus is on the effect of cobalt oxide powder in the carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fine TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under flowing argon atmosphere. Changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. Titanium-cobalt-oxygen based oxide powder desalted at $600^{\circ}C$ had a mixture of $TiO_2\;and\;Co_{3}O_4$. And the one desalted at $800^{\circ}C$ had a mixture of $TiO_2\;and\;CoTiO_3$. In the case of the former powder, the reduction of cobalt oxide powder in the titanium-cobalt-oxygen based oxide powder occurred at lower temperature than the latter one. However, the carbothermal reduction of titanium dioxide powder in the titanium-cobalt-oxygen based oxide powder with a mixture of $TiO_2\;and\;Co_{3}O_4$ occurred at higher temperature than the one with a mixture of $TiO_2\;and\;CoTiO_3$. And also, the former powder showed a lower TiC formation ability than the latter one.

Oxygen Transfer Characteristics & Pure Oxygen Application Study on Circulation Flow Rate of the JLB (Jet Loop Bioreactor) (Jet 폭기 시스템의 순환유량에 따른 산소전달 특성 및 순산소 적용성 검토)

  • Park, Noh-Back;Song, Yong-Hyo;Pack, June-Gue;Jun, Hang-Bae
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.896-901
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    • 2009
  • In this study, in order to apply the air and pure oxygen in the Jet Loop Reactor (JLB) in which the oxygen transfer rate is high, differentiate the operation mode according to each air flowrate and liquid flowrate and investigate the oxygen transfer characteristic, an experiment was carried out. The oxygen concentration with the air flowrate ($Q_g$) and liquid flowrate ($Q_L$) was identical but the oxygen transfer coefficient ($K_L{\cdot}a$) is linear depending on degree of two factors. The width of an increase is small in $0.1min^{-1}$ when the air flowrate is 0.2 L/min with increasing the liquid flowrate. Whereas, the increment was exposed to be very high for $1.5min^{-1}$ when the air flowrate was 5 L/min. In the experiments using the pure oxygen, it was 30 mg/L of oxygen concentration finally and it was 3.5 times than using the air. But the time reached the saturated concentration was similar to using the air, and $K_L{\cdot}a$ was similar to using the air too. Analysis between two independent variable and oxygen transfer of the correlation is the same model like $K_L{\cdot}a={0.0161Q_L}^{1.5371}{Q_g}^{0.5433}$ using with coefficient non linear regression analysis. It was resulted that the liquid flowrate were approximately three times than air flowrate on effect to oxygen transfer rate.

The Effect of Oxygen Concentration in Hot Exhaust Gas on the $NO_{x}$ Emission of Diffusion Flame in Exhaust Gas (고온 배기가스의 산소농도가 배기가스이용 확산화염의 $NO_{x}$ 발생에 미치는 영향)

  • Sohn, H.S.;Jang, S.W.;Choi, D.S.;Kim, H.Y.
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.115-120
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    • 2001
  • The present study examined the possibility of $NO_{x}$ reduction in the high temperature industrial furnaces. duct burner of gas turbine cogeneration and two-stage gas turbine combustor. The experimental study was carried out for the diffusion flame of second stage combustor with the variations of oxygen concentration and supplying rate of hot exhaust gas from first stage combustor. It also examined the flammability range and $NO_{x}$ formation of the second stage combustor in which the fuel is supplying into the mixture of oxygen hot exhaust gas from first stage combustor. The results show that the enrichment of oxygen and increase of exhaust gas lead to increase the $NO_{x}$ up to 50 ppm with 23% $O_{2}$ condition.

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Effect of argon flow on the quality of Czochralski silicon crystal (쵸크랄스키 실리콘 단결정의 특성에 미치는 아르곤 유동의 영향)

  • 김정민;이홍우;최준영;유학도
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.10 no.2
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    • pp.91-95
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    • 2000
  • The effects of argon gas flow on the axial temperature gradient near the interface, the oxygen concentration, and the radial oxygen uniformity was investigated for 8-inch CZ silicon growth. As argon flow rate was increased, the temperature gradient was increased in the crystal near the crystavmelt interface and the oxygen content in the crystal was decreased. But the radial oxygen uniformity was deteriorated. It was found that argon flow is one of the important growing parameters to affect the quality of crystals such as oxygen content and uniformity.

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