• Title/Summary/Keyword: $H_2$ oxidation

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High Temperature Oxidation of Ti-6Al-4V, Ti-4Fe, Ti-(1,2)Si Alloys (Ti-6Al-4V, Ti-4Fe, Ti-(1,2)Si합금의 고온산화)

  • 박기범;이동복
    • Journal of the Korean institute of surface engineering
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    • v.34 no.2
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    • pp.135-141
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    • 2001
  • Arc-melted Ti-6Al-4V, Ti-4Fe and Ti-(1,2) Si alloys were oxidized at 700, 800, 900 and $1000^{\circ}C$ in air. The oxidation resistance of Ti-4Fe was comparable to that of Ti-6Al-4V, while the oxidation resistance of Ti-(1,2) Si was superior to that of Ti-6Al-4V. Ti-2Si displayed the best oxidation resistance among the four alloys, but failed after oxidation at $1000^{\circ}C$ for 17h. The oxide scale formed on Ti-6Al-4V, Ti-4Fe and Ti-(1,2)Si consisted of ($TiO_2$ and a small amount of $Al_2$$O_3$), ($TiO_2$ and a small amount of dissolved iron), and ($TiO_2$ plus a small concentration of amorphous $SiO_2$), respectively. The oxide grains of the surface scale of the four alloys were generally fine and round.

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Degradation of TCE by Persulfate Oxidation with Various Activation Methods (heat, Fe2+, and UV) for ex-situ Chemical Oxidation Processes (Ex-situ 화학적 산화처리 적용을 위하여 다양하게 활성화(heat, Fe2+, UV)된 persulfate를 이용한 TCE 분해에 대한 연구)

  • Kim, Han-Sol;Do, Si-Hyun;Park, Ki-Man;Jo, Young-Hoon;Kong, Sung-Ho
    • Journal of Soil and Groundwater Environment
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    • v.17 no.6
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    • pp.43-51
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    • 2012
  • Rreactivity of persulfate (PS) for oxidation of TCE under various conditions such as heat, $Fe^{2+}$, and UV was investigated. It was found that degradation rate of TCE increased with increasing temperature from 15 to $35^{\circ}C$. At pH 7.0, the rate constants (k) at 15, 25, 30, and $35^{\circ}C$ were 0.07, 0.30, 0.74, and $1.30h^{-1}$, respectively. For activation by $Fe^{2+}$, removal efficiency of TCE increased with increasing $Fe^{2+}$ concentration from 1.9 mM to 11 mM. The maximum removal efficiency of TCE was approximately 85% when pH of the solution dropped from 7.0 to 2.5. Degradation of TCE by UV-activated PS was the most effective, showing that the degradation rate of TCE increased with inreasing PS dosage; the rate constants (k) at 0.5, 2.5, and 10 mM were 34.2, 40.5, and $55.9h^{-1}$, respectively. Our results suggest that PS activation by UV/PS process could be the most effective in activation processes tested for TCE degradation. For oxidation process by PS, however, pH should be observed and adjusted to neutral conditions (i.e., 5.8-8.5) if necessary.

Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of Butanone and Uncatalyzed Oxidation of Cychlohexanone by Cerium(IV) in Acid Sulphate Medium

  • Sharma, Priyamvada;Hemkar, Shalini;Khandelwal, C.L.;Sharma, P.D.
    • Journal of the Korean Chemical Society
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    • v.56 no.1
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    • pp.28-33
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    • 2012
  • The kinetics of ruthenium(III) chloride catalyzed oxidation of butanone and uncatalyzed oxidation of cyclohexanone by cerium(IV) in sulphuric acid medium have been studied. The kinetic rate law(I) in case of butanone conforms to the proposed mechanism. $$-\frac{1}{2}\frac{d[Ce^{IV}]}{dt}=\frac{kK[Ru^{III}][butanone]}{1+K[butanone]}$$ (1). However, oxidation of cyclohexanone in absence of catalyst accounts for the rate eqn. (2). $$-\frac{1}{2}\frac{[Ce^{IV}]}{dt}=\frac{(k_1+k_1K^'[H^+])[Ce^{IV}][Cyclohexanone]}{1+K_3[HSO_4^-]}$$ (2) Kinetics and activation parameters have been evaluated conventionally. Kinetically preferred mode of reaction is via ketonic and not the enolic forms.

High Temperature Corrosion of Cr(III) Coatings in N2/0.1%H2S Gas

  • Lee, Dong Bok;Yuke, Shi
    • Journal of the Korean institute of surface engineering
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    • v.52 no.3
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    • pp.111-116
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    • 2019
  • Chromium was coated on a steel substrate by the Cr(III) electroplating method, and corroded at $500-900^{\circ}C$ for 5 h in $N_2/0.1%H_2S-mixed$ gas to study the high-temperature corrosion behavior of the Cr(III) coating in the highly corrosive $H_2S-environment$. The coating consisted of (C, O)-supersaturated, nodular chromium grains with microcracks. Corrosion was dominated by oxidation owing to thermodynamic stability of oxides compared to sulfides and nitrides. Corrosion initially led to formation of the thin $Cr_2O_3$ layer, below which (S, O)-dissolved, thin, porous region developed. As corrosion progressed, a $Fe_2Cr_2O_4$ layer formed below the $Cr_2O_3$ layer. The coating displayed relatively good corrosion resistance due to formation of the $Cr_2O_3$ scale and progressive sealing of microcracks.

High-temperature oxidation of Ti3(Al,Si)C2 nano-laminated compounds in air

  • Lee, Hwa-Shin;Lee, Dong-Bok
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2007.11a
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    • pp.147-148
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    • 2007
  • The compound, Ti3(Al,Si)C2, was synthesized by hot pressing a powder mixture of TiCX, Al and Si. Its oxidation at 900 and 1000 oC in air for up to 50 h resulted in the formation of rutile-TiO2, -Al2O3 and amorphous SiO2. During oxidation, Ti diffused outwards to form the outer TiO2 layer, and oxygen was transported inwards to form the inner mixed layer.

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Electrical Characterization of MOS (metal-oxide-semiconductor) Capacitors on Plasma Etch-damaged 4H-Silicon Carbide (플라즈마 에칭으로 손상된 4H-실리콘 카바이드 기판위에 제작된 MOS 커패시터의 전기적 특성)

  • 조남규;구상모;우용득;이상권
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.4
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    • pp.373-377
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    • 2004
  • We have investigated the electrical characterization of metal-oxide-semiconductor (MOS) capacitors formed on the inductively coupled plasma (ICP) etch-damaged both n- and p-type 4H-SiC. We found that there was an effect of a sacrificial oxidation treatment on the etch-damaged surfaces. Current-voltage and capacitance-voltage measurements of these MOS capacitors were used and referenced to those of prepared control samples without etch damage. It has been found that a sacrificial oxidation treatment can improve the electrical characteristics of MOS capacitors on etch-damaged 4H-SiC since the effective interface density and fixed oxide charges of etch-damaged samples have been found to increase while the breakdown field strength of the oxide decreased and the barrier height at the SiC-SiO$_2$ interface decreased for MOS capacitors on etch-damaged surfaces.

Protective Ability of Ethanol Extracts of Hypericum scabroides Robson & Poulter and Hypericum triquetrifolium Turra against Protein Oxidation and DNA Damage

  • Kizil, Goksel;Kizil, Murat;Ceken, Bircan
    • Food Science and Biotechnology
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    • v.18 no.1
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    • pp.130-136
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    • 2009
  • The present study was conducted to determine the protective ability of the ethanol extracts of Hypericum scabroides Robson & Poulter (HS) and Hypericum triquetrifolium Turra (HT) against the protein oxidation and DNA damage induced by Fenton system. The ability of HS and HT to prevent oxidative damage to bovine serum albumin (BSA) induced by $Fe^{3+}/H_2O_2$ and ascorbic acid was investigated. The ethanol extracts of HS and HT at different concentrations ($50-1,000{\mu}g/mL$) efficiently prevented protein oxidation induced by hydroxy radical as assayed by protein oxidation markers including protein carbonyl formation (PCO) and polyacrylamide gel electrophoresis. The effect of ethanol extracts of HS and HT on DNA cleavage induced by UV-photholysis of $H_2O_2$ using pBluescript M13+ plasmid DNA were investigated. These extracts significantly inhibited DNA damage induced by reactive oxygen species (ROS). Therefore, HS and HT extracts may be useful in the food industry as effective synthetic antioxidants.

Competitive electrochemical oxidation of reformate gas in SOFCs (고체 산화물 연료전지 음극에서 개질 가스의 경쟁적 전기화학 반응)

  • Kim, Yong-Min;Bae, Joong-Myeon;Bae, Gyu-Jong;Kim, Jung-Hyun;Lee, Chang-Bo
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.05a
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    • pp.5-8
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    • 2008
  • SOFC (Solid oxide fuel cell) has an advantage in the term of fuel flexibility, comparing with other kinds of fuel cells. In SOFC and fuel reformer cooperation system, the reformate gas with the various $H_2$/CO ratios is delivered into the anode of SOFC. In this situation, electrochemical oxidation reactions of the reformate gas in the anode are complex and competitive. In this paper, the effects of the composition of $H_2$ and CO on the overall electrochemical oxidation at Ni-YSZ anode are studied by testing the open circuit voltage (OCV) and current-voltage characteristics of single cells.

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The effect of Rh/Ce/Zr additives on the redox cycling of iron oxide for hydrogen storage (산화철의 환원-산화 반응을 이용한 수소저장에 미치는 Rh/Ce/Zr의 효과)

  • Lee, Dong-Hee;Cha, Kwang-Seo;Park, Chu-Sik;Kang, Kung-Soo;Kim, Young-Ho
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.49-52
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    • 2007
  • We investigated hydrogen storage and production properties using redox system of iron oxide($Fe_{3}O_{4}$ + $4H_{2}$ ${\leftrightarrows}$ 3Fe + $4H_{2}O$) modified with rhodium, ceria and zirconia under atmospheric pressure. Reduction of iron oxide with hydrogen(hydrogen storage) and re-oxidation of reduced iron oxide with steam(hydrogen evolution) was carried out using a temperature programmed reaction(TPR) technique. On the temperature programmed studies, the effects of amounts of cerium and zirconium on the re-oxidation rate of partial reduced iron oxides were increased with increasing metal additives amount, but the rhodium amount showed little effect on the re-oxidation rate. On the thermal studies, the re-oxidation rates were enhanced with increasing temperature(300 $^{\circ}C$ < 350 $^{\circ}C$).

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A Study on the Oxidation Characteristics of p-Cresol on Pt Anode (백금전극(白金電極)에 의한 파라크레졸의 양극전해(陽極電解) 산화특성(酸化特性))

  • Kim, Hong-Soo;Nam, Jeong-Woo
    • Journal of the Korean Applied Science and Technology
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    • v.7 no.2
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    • pp.47-53
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    • 1990
  • The electrochemical oxidation behavior of p-cresol on platinum anode had been investigated by cyclic voltammetric method for the variation of concentration, scan rate of potential, temperature and pH of electrolyte. The oxidation potential of p-cresol was dependent on the electrolyte until the pH=11.5, but in basic solution over its, it was held at o.40V(vs. SCE). A diffusion was rate determining step of oxidation as irreversible reaction by the transfer atone electron. The current of peak was proportional to concentration of p-cresol until the 0.1N and optimum concentration was found to be about 0.1N. The activation energy was calculated for 5.8kcal/mol from the plot of log $I_l$ vs. 1/T.