• Title, Summary, Keyword: Oxidation

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A Effect of the Oxidation Process on the Lifetime Properties of Ag-CdO Contact Materials (산화 방식이 Ag-CdO계 전기접점재료의 수명 특성에 미치는 영향)

  • Kwon, Gi-Bong;Nam, Tae-Woon
    • Journal of Korea Foundry Society
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    • v.25 no.6
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    • pp.233-239
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    • 2005
  • Contact material is widely used in the field of electrical parts. Ag-CdO has a good wear resistance and stable contact resistance. We studied a lifetime of Ag-CdO material because of getting better properties of Ag-CdO using Post-oxidation. The experimental procedure were melting using high frequency induction, heat treatment, rolling and internal oxidation. And we experimented on difference process, Post-oxidaion. Then we tested a lifetime and analysed. We obtained the optimizing oxidation temperature was $750^{\circ}C$. Using Pre-oxidation, coarse oxide and depleted oxidation layer existed but finer oxides were existed and depleted oxidation layer was not using Post-oxidation. In Post-oxidation, The density was 10 $g/cm^{3}$, the hardness was Hv 80 and the adhesive strength was 9000N. The specimen of Post-oxidation had better lifetime properties than that of Pre-oxidation. We predicted that the lifetime of Post-oxidation specimen is more longer twice than that of Pre-oxidation one.

Improvement of Biomass Degradation by Fenton Oxidation and Reusability of the Fenton Oxidation Solution (펜톤산화에 의한 바이오매스 분해향상과 펜톤산화 용액 재사용 평가)

  • Jeong, So-Yeon;Lee, Jae-Won
    • New & Renewable Energy
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    • v.16 no.4
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    • pp.83-91
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    • 2020
  • In this study, the reusability of the Fenton oxidation solution was evaluated to reduce the cost of the pretreatment process. Biomass was sequential subjected to Fenton oxidation-hydrothermal treatment and enzymatic hydrolysis to produce monosaccharides. The liquid solution recovered after Fenton oxidation contained OH radicals with a concentration of 0.11 mol/L. This liquid solution was reused for a new Fenton oxidation reaction. After Fenton oxidation, hydrothermal treatment was performed under the same conditions as before, and 9.34-13.63 g/L of xylose was detected. This concentration was slightly lower than that of a fresh Fenton oxidation solution (16.51 g/L) but was higher than that obtained by hydrothermal treatment without Fenton oxidation (2.72 g/L). The degradation rate during hydrothermal pretreatment involving Fenton oxidation was 36.02%, which decreased (29.24-31.05%) slightly when the liquid solution recovered after Fenton oxidation was reused. However, the degradation rate increased compared to that measured from hydrothermal treatment without Fenton oxidation (15.21%). Moreover, the yield after enzyme hydrolysis decreased in the following order: fresh Fenton oxidation-hydrothermal treatment (89.64%) > Fenton oxidation with reused solution-hydrothermal treatment (74.84%) > hydrothermal treatment without Fenton oxidation (32.05%).

A Study on N2O Direct Oxidation Process with Re-oxidation Annealing for the Improvement of Interface Properties in 4H-SiC MOS Capacitor

  • Cho, Doohyung;Park, Kunsik;Yoo, Seongwook;Kim, Sanggi;Lee, Jinhwan;Kim, Kwangsoo
    • Journal of the Korean Physical Society
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    • v.71 no.3
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    • pp.150-155
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    • 2017
  • The effect of $N_2O$ direct oxidation processes with re-oxidation on $SiC/SiO_2$ interface characteristics has been investigated. With different oxidation and post oxidation annealing (POA) processes, the flat-band voltage, effective dielectric charge density, and interface trap density are obtained from the capacitance-voltage curves. For the proposed $N_2O$ direct oxidation processes with re-oxidation, oxides were grown in $N_2O$ ambient, diluted in high-purity $N_2$ to 10% concentration, for 5 h at $1230^{\circ}C$. After the growth, some samples were annealed additionally at $1200^{\circ}C$ in $O_2$ or $H_2O$ for 20 min. $N_2O$ direct oxidation with re-oxidation processes was confirmed that SiC/SiO2 interface properties and dielectric stability have better performance than with other conventional oxidation processes. This oxidation technique is expected to improve gate dielectric stability for application to SiC MOS devices; in particular, it can be used to obtain high-quality $SiC/SiO_2$ interface properties.

INVESTIGATION OF SOOT OXIDATION CHARACTERISTICS IN A SIMULATED DIESEL PARTICULATE FILTER

  • Lee, H.S.;Chun, K.M.
    • International Journal of Automotive Technology
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    • v.7 no.3
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    • pp.261-267
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    • 2006
  • Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Carbon oxidation characteristics were investigated by temperature programmed oxidation(TPO) method as well as constant temperature oxidation(CTO) with a flow reactor including porous bed. The activation energy of carbon oxidation was increasing with temperature and had two different constant values in the early and the later stage of the oxidation process respectively in TPO experiment. Kinetic constants were derived and the reaction mechanisms were assumed from the experimental results and a simple reaction scheme was proposed, which approximately predicted the overall oxidation process in TPO as well as CTO.

Liquid Phase Oxidation of Xylenes: Effects of Water Concentration and Alkali Metals

  • Jhung, Sung-Hwa;Lee, Ki-Hwa;Park, Youn-Seok
    • Bulletin of the Korean Chemical Society
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    • v.23 no.1
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    • pp.59-64
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    • 2002
  • A facile and precise batch oxidation reaction system allows continuous monitoring of the oxidation rate and cumulated oxygen conversion of xylenes, and the side reactions to carbon monoxide and carbon dioxide may also be studied. The oxidation reaction can be analyzed precisely with the rate and amount of oxygen consumed. The reaction reveals that 4-carboxybenzaldehyde is an unstable intermediate of p-xylene oxidation as the reaction proceeds instantaneously from p-toluic acid to TPA (terephthalic acid). The alkali metals accelerate oxidation, even though they retard the reaction initially. The oxidation rate increases with decreasing water concentration. However, in the later part of reaction, the reactivity decreases a bit if the water concentration is very low. This retarding effect of water can be overcome partly by the addition of potassium. The oxidation of o-xylene, compared with the oxidation of p-xylene and m-xylene, proceeds quite fast initially, however, the oxidation rate of xylene isomers in the later stage of reaction is in the order of p-xylene > mxylene > o-xylene.

Prediction Modeling of Unburned Hydrocarbon Oxidation in the Exhaust Port of a Propane-Fueled SI Engine (프로판 엔진의 배기 포트에서 탄화수소 산화 예측을 위한 모델링)

  • 이형승;박종범;최회명;민경덕;김응서
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.2
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    • pp.33-40
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    • 2000
  • In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, a numerical simulation was performed with 3-dimensional flow model and oxidation mechanism optimized for port oxidation. To predict the exhaust and oxidation process with consideration of flow, mixing, and temperature, 3-dimensional flow model and HC oxidation model were used with a commercial computational program, STAR-CD. The flow model were with moving grid for valve motion, which could predict the change of flow field with respect to valve lift. Optimization was performed to predict the HC oxidation with temperature range of 1200~1500K, low HC and oxygen concentration, existence of intermediate species, as typical in port oxidation. The constructed model could predict the port oxidation process with oxidation degree of 14~48% according to the engine operation conditions.

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Effect of Organic Acids on Cr(III) Oxidation by Mn-oxide

  • Chung, Jong-Bae
    • Applied Biological Chemistry
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    • v.41 no.4
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    • pp.241-245
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    • 1998
  • Two oxidation states of chromium commonly occur in natural soil/water systems, Cr(III) and Cr(VI). The oxidized form, Cr(VI), exists as the chromate ion and is more mobile and toxic than Cr(III). Therefore oxidation of Cr(III) by various Mn-oxides in natural systems is a very important environmental concern. Organic substances can inhibit the Cr(III) oxidation by binding, Cr(III) strongly and also by dissolving Mn-oxides. Most of Cr(III) oxidation studies were carried out using in vitro systems without organic substances which exist in natural soil/water systems. In this study effect of organic acids - oxalate and pyruvate - on Cr(III) oxidation by $birnessite({\delta}-MnO_2)$ was examined. The two organic acids significantly inhibited Cr(III) oxidation by birnessite. Oxalate showed more significant inhibition than pyruvate. As solution pH was lowered in the range of 3.0 to 5.0, the Cr(III) oxidation was more strongly depressed. Addition of more organic acids reduced the Cr(III) oxidation mare extensively. Different inhibition effects by the organic acids could be due to their ability of reductive dissolution of Mn-oxides and/or Cr(III) binding. Organic acids dissolved Mn-oxide during the Cr(III) oxidation by the oxide, Dissolution by oxalic acid was much greater than that by pyruvate, and the dissolution was more extensive at lower pH. Inhibition of Cr(III) oxidation was parallel to the dissolution of Mn-oxide by organic acids. Although the effect of Cr(III) binding by organic acids on Cr(III) oxidation is not known yet, Mn-oxide dissolution by organic acids could be a main reason for the inhibition of Cr(III) oxidation by Mn-oxide in presence of organic acids. Thus oxidation of Cr(III) to Cr(VI) by various Mn-oxides in natural systems could be much less than the oxidation estimated by in vitro studies with only Cr(III) and Mn-oxides.

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Oxidation Rates of TiAlLaN Thin Films Deposited by Ion Plating (이온플레이팅법으로 제조된 TiAlLaN계 박막의 산화속도)

  • Seo Sung Man;Lee Kee Sun;Lee Kee-Ahn
    • Korean Journal of Materials Research
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    • v.14 no.3
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    • pp.163-167
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    • 2004
  • TiAl(La)N thin films were oxidized in vacuum of about 7 Pa to reduce the oxidation of WC-Co as a substrate. The oxidation rate constants of the thin films were quantified by an assumption of parabolic oxidation. Increasing AI content significantly decreased the parabolic oxidation rate constant. A simultaneous addition of AI and La was more effective to reduce the oxidation rate. The parabolic oxidation rate constant of $Ti_{0.66}$ $Al_{0.32}$ $La_{ 0.02}$N thin film at 1273 K showed about ten times lower than that of TiN. The addition of a small amount of La with Al induced the preferential formation of dense $\alpha$ $-Al_2$$O_3$ film in oxide film, leading to the abrupt reduction of oxidation rate.

Oxidation Behavior of WC-Co Hardmetal (WC-Co 초경합금의 산화거동)

  • 이길근;권한상;하국현
    • Journal of Korean Powder Metallurgy Institute
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    • v.11 no.2
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    • pp.111-117
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    • 2004
  • The oxidation behavior of 91 WC-9Co hardmetal in weight percentage has been studied in the present work as a part of the development of recycling process. The morphological and compositional changes of the WC-Co hardmetal with oxidation time at 90$0^{\circ}C$ were analyzed by using surface observation and X-ray diffraction. respective]y. As the oxidation time increased, the WC-Co hardmetal was continuously expanded to form porous oxide mixtures of $CoWO_4$ and $WO_3$. The morphology of porous oxide mixture was basically dependent on initial shape of the WC-Co hardmetal. From thermo-gravimetric (TG) analysis, it was found that the oxidation rate was increased with increasing oxidation temperature and oxygen content in the flowing atmospheric gas. The fraction of oxidation versus time curves showed S-curve relationship at a given of oxidation temperature. These oxidation behaviors of the WC-Co hardmetal were discussed in terms of previously proposed kinetic models.

Evaluation of Oxidation Stability for Diesel Engine Oil by Hot-Tube Oxidation Test (Hot-Tube Oxidation Test에 의한 디젤엔진오일의 산화안정성 평가)

  • 정근우;조원오;김영운;서인옥;임수진
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.175-180
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    • 1998
  • This paper describes evaluation of oxidation stability for diesel engine oils by Hot-tube oxidation tester at high temperature. Evaluation was rated by visual inspection of lacquer in capillary glass tube and TAN determination of used oil. Air, NO$_2$-air and SO$_2$-air mixed gases were used as oxidizing gas. One oil which has low oxidation stability is selected and reformulated by addition of some additives such as antioxidant, detergent and disperant to improve oxidation stability. As a results of reformulation, antioxidant and detergent was effective for improvement of high temperture oxidation stability on diesel engine oil.

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