• 제목/요약/키워드: Carbon oxidation

검색결과 1,102건 처리시간 0.032초

Influence of Electric Potential on Structure and Function of Biofilm in Wastewater Treatment Reactor : Bacterial Oxidation of Organic Carbons Coupled to Bacterial Denitrification

  • NA BYUNG KWAN;SANG BYUNG IN;PARK DAE WON;PARK DOO HYUN
    • Journal of Microbiology and Biotechnology
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    • 제15권6호
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    • pp.1221-1228
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    • 2005
  • Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

탄소섬유의 양극산화가 탄소섬유 강화 복합재료의 기계적 계면 특성에 미치는 영향 (Effect of Anodized Carbon Fiber Surfaces on Mechanical Interfacial Properties of Carbon Fibers-reinforced Composites)

  • 박수진;오진석;이재락
    • Composites Research
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    • 제15권6호
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    • pp.16-23
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    • 2002
  • 본 연구에서는 양극산화 처리에 따른 고강도 PAN계 탄소섬유의 표면 특성 변화가 기계적 계면 물성에 미치는 영향을 조사하였다. 탄소섬유의 표면성질은 산.염기도, SEM, XPS, 그리고 접촉각 측정을 통하여 알아보았으며, 복합재료의 기계적 계면 특성은 ILSS와 $K_{IC}$를 통하여 고찰하였다. 탄소섬유 표면의 산도와 $O_{ls}/C_{IC}$가 증가하였는데, 이는 산소관능기의 발달에 기인하고, 양극산화된 탄소섬유의 표면자유에너지의 증가는 극성요소의 증가에 기인하는 것으로 사료된다. ILSS와 $K_{IC}$ 같은 기계적 계면 성질은 양극산화로 향상되어졌는데, 이러한 결과는 좋은 젖음성이 최종 복합재료의 섬유와 에폭시 수지 매트릭스 사이의 계면결합력을 증가시기는 중요한 역할을 하기 때문으로 사료된다.

산화억제제 첨가에 의한 탄소/탄소 복합재료의 물성에 관한 연구: 9. 복합재료의 충격특성에 관한 연구 (Influence of Oxidation Inhibitor on Carbon-Carbon Composites: 9. Studies on Impact Properties of the Composites)

  • 박수진;서민강;이재락
    • Composites Research
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    • 제16권3호
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    • pp.41-48
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    • 2003
  • 본 연구에서는 고온 산화분위기 하에서 탄소/탄소 복합재료의 내산화 특성 향상을 위해 사용된 이규화 몰리브덴(MoSi$_2$)의 함량(0. 4, 12. 그리고 20 wt%)에 따른 복합재료의 충격특성에 관하여 고찰하였다. 결과로서, MoSi$_2$가 함침된 탄소/탄소 복합재료는 이를 함유하지 않은 것에 비하여 충격특성 향상의 원인이 되는 탄소섬유와 매트릭스 수지간의 계면결합력 증가를 가져왔으며, 특히 12 wt% MoSi$_2$가 현재의 시스템에서 가장 우수한 충격특성을 나타내었다. 이는 복합재료 내의 탄소섬유, 필러, 그리고 매트릭스 수지간의 계면 접착력의 증가를 가져오는 90$0^{\circ}C$ 전후에서 MoSi$_2$의 취성­연성 전이(BDT) 작용 때문이라 사료된다.

Electrodeposited NiCu Alloy Catalysts for Glucose Oxidation

  • Lim, Ji-Eun;Ahn, Sang Hyun;Jang, Jong Hyun;Park, Hansoo;Kim, Soo-Kil
    • Bulletin of the Korean Chemical Society
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    • 제35권7호
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    • pp.2019-2024
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    • 2014
  • NiCu alloys have been suggested as potential candidates for catalysts in glucose oxidation. In this study, NiCu alloys with different compositions were prepared on a glassy carbon substrate by changing the electrodeposition potential to examine the effect of Ni/Cu ratios in alloys on catalytic activity toward glucose oxidation. Cyclic voltammetry and chronoamperometry showed that NiCu alloys had higher catalytic activity than pure Ni and Cu catalysts. Especially, Ni59Cu41 had superior catalytic activity, which was about twice that of Ni at a given oxidation potential. X-ray analyses showed that the oxidation state of Ni in NiCu alloys was increased with the content of Cu by lattice expansion. Ni components in alloys with higher oxidation state were more effective in the oxidation of glucose.

Hafnium Carbide Protective Layer Coatings on Carbon/Carbon Composites Deposited with a Vacuum Plasma Spray Coating Method

  • 유희일;김호석;홍봉근;신의섭;문세연
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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    • pp.237.2-237.2
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    • 2016
  • A pure hafnium-carbide (HfC) coating layer was deposited onto carbon/carbon (C.C) composites using a vacuum plasma spray system. By adopting a SiC buffer layer, we successfully integrated C.C composites with a $100-{\mu}m-thick$ protective coating layer of HfC. Compared to the conventional chemical vapor deposition process, the HfC coating process by VPS showed increased growth rate, thickness, and hardness. The growth behavior and morphology of HfC coatings were investigated by FE-SEM, EDX, and XRD. From these results, it was shown that the addition of a SiC intermediate layer provided optimal surface conditions during the VPS procedure to enhance adhesion between C.C and HfC (without delamination). The thermal ablation test results shows that the HfC coating layer perfectly protected inner C.C layer from thermal ablation and oxidation. Consequently, we expect that this ultra-high temperature ceramic coating method, and the subsequent microstructure that it creates, can be widely applied to improve the thermal shock and oxidation resistance of materials under ultra-high temperature environments.

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The Determination of Dopamine in the Presence of Ascorbic Acid at the Modified Glassy Carbon Electrode with Phytic Acid and Single-Walled Carbon Nanotubes

  • Bae, Si-Ra;Jeong, Hae-Sang;Jeon, Seung-Won
    • Bulletin of the Korean Chemical Society
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    • 제28권12호
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    • pp.2363-2368
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    • 2007
  • A glassy carbon electrode (GCE) modified with phytic acid (PA) and single-walled carbon nanotubes (SWNTs) were investigated by voltammetric methods in buffer solution. The PA-SWNTs/GCE-modified electrode demonstrated substantial enhancements in electrochemical sensitivity and selectivity towards dopamine (DA) in the presence of L-ascorbic acid (AA). The PA-SWNTs films promoted the electron transfer reaction of DA, while the PA film, acting as a negatively charged linker, combined with the positively charged DA to induced DA accumulation in the film at pH under 7.4. However, the PA film restrained the electrochemical response of the negatively charged AA due to the electrostatic repulsion. The anodic peak potentials of DA and AA could be separated by electrochemical techniques, and the interferences from AA were effectively eliminated in the DA determination. Linear calibration plots were obtained in the DA concentration range of 0.1-10 μM and the detection limit of the DA oxidation current was determined to be 0.06 μM at a signal-to-noise ratio of 3. The results indicated that the modified electrode is used to determine DA without interference from AA.

탄소/탄소 복합재료의 마찰 및 마모 거동과 신경회로망에의 적용에 관한 연구 (Friction and Wear Behavior of Carbon/carbon Composite Materials and its Application to a Neural Network)

  • 류병진;윤재륜;권익환
    • Tribology and Lubricants
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    • 제10권4호
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    • pp.13-26
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    • 1994
  • Effects of resin contents, number of carbonization, graphitization, sliding speed, and oxidation on friction and wear behavior of carbon/carbon composite materials were investigated. Friction and wear tests were carried out under various sliding conditions. An experimental setup was designed and built in the laboratory. Stainless steel disks were used as the counterface material. Friction coefficient, emperature, and wear factor were measured with a data acquisition system. Wear surfaces were observed by the scanning electron microscope. It has been shown that the average friction coefficient was increased with the sliding speed in the range of 1.43~6.10 m/s, but it as decreased in the range of 6.10~17.35 m/s. Specimens prepared by different numbers of carbonization. showed variations in friction coefficient and friction coefficient of the graphitized specimen was the highest. Friction coefficients depended on contribution of the plowing and adhesive components. As the number of carbonization was increased, wear factor was reduced. Wear factor of the graphitized specimens dropped further. In the case of graphitized specimens, sliding speed had a large influence on wear behavior. When the tribological experiments were conducted in nitrogen atmosphere, the wear factor was decreased to two thirds of the wear factor obtained in air. It is obvious that the difference was affected by oxidation. Results of friction and wear tests were applied to a neural network system based on the backpropagation algorithm. A neural network may be a valuable tool for prediction of tribological behavior of the carbon/carbon composite material if ample data are present.

Protective SiC Coating on Carbon Fibers by Low Pressure Chemical Vapor Deposition

  • Bae, Hyun Jeong;Kim, Baek Hyun;Kwon, Do-Kyun
    • 한국재료학회지
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    • 제23권12호
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    • pp.702-707
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    • 2013
  • High-quality ${\beta}$-silicon carbide (SiC) coatings are expected to prevent the oxidation degradation of carbon fibers in carbon fiber/silicon carbide (C/SiC) composites at high temperature. Uniform and dense ${\beta}$-SiC coatings were deposited on carbon fibers by low-pressure chemical vapor deposition (LP-CVD) using silane ($SiH_4$) and acetylene ($C_2H_2$) as source gases which were carried by hydrogen gas. SiC coating layers with nanometer scale microstructures were obtained by optimization of the processing parameters considering deposition mechanisms. The thickness and morphology of ${\beta}$-SiC coatings can be controlled by adjustment of the amount of source gas flow, the mean velocity of the gas flow, and deposition time. XRD and FE-SEM analyses showed that dense and crack-free ${\beta}$-SiC coating layers are crystallized in ${\beta}$-SiC structure with a thickness of around 2 micrometers depending on the processing parameters. The fine and dense microstructures with micrometer level thickness of the SiC coating layers are anticipated to effectively protect carbon fibers against the oxidation at high-temperatures.

입자상 활성탄의 흡착과 재생에 의한 PCBs 오염제거 (Decontamination of PCBs by Hybrid Adsorption/Regeneration on Granular Activated Carbon)

  • 홍용표;최종하
    • 대한화학회지
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    • 제46권2호
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    • pp.117-124
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    • 2002
  • 활성탄에 흡착되어 있는 유기질을 처리하기 위하여 역류산화반응이 개발되었고 그것에 대한 평가가 이루어 졌다. 역류산화반응이란 산소의 흐름과 반대로 이동하는 자발적인 불꽃을 이용하여 유기질을 파괴 및 제거함과 동시에 폐활성탄을 재생하는 방법이다. 본 연구를 통하여 얻어진 실험결과를 고찰해 보면, 활성탄의 질량손실과 불꽃의 온도가 산소의 흐름속도에 절대적으로 의존하였고, 재생탄의 비표면적이 거의 완전히 회복되었으며, 특히 활성탄에 흡착되어 있는 열에 안정한 PCBs를 거의 완전히 파괴 및 제거(99.99%이상)할 수 있었다.

${CO}_2$ gas및 공기중에서 피치계 탄소섬유의 산화거동 (The Oxidation Behavior of Pitch based Carbon Fibers in ${CO}_2$ Gas and Air)

  • 노재승;서동수
    • 한국재료학회지
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    • 제7권2호
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    • pp.121-128
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    • 1997
  • 이방성과 등방성을 갖는 두 종류의 피치계 탄소섬유를 TGA장치를 이용하여 $CO_{2}$gas와 공기중에서 등온산화반응을 실시하였다. $CO_{2}$ gas보다 공기중에서의 산화가 훨씬 빠르게 일어났으며, $600^{\circ}C$공기중에서 등방성 T-10IS섬유는 이방성 HM-60섬유보다 23.9배나 빠른 산화속도를 보였다. 실험적으로 구한 활성화에너지를 저온에서 36-56Kcal/mole의 값을 가지며, 고온에서는 6-13Kcal/mole의 값을 나타내었다. 반응기구(zone 1,2,3)의 천이도는 T-10IS섬유보다 HM-60 섬유가 높았으며, 공기중에서보다 $CO_{2}$ gas분위기에서 더 높게 나타났다. SEM으로 관찰된 표면상변화로부터 탄소섬유의 산화반응은 섬유의 결함을 따라 진행된다는 것을 알 수 있었다.

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