• Nuclear Engineering and Technology
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• 제43권4호
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• pp.391-398
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• 2011

The U metal chips generated in developing nuclear fuel and a gamma radioisotope shield have been stored under immersion of water in KAERI. When the water of the storing vessels vaporizes or drains due to unexpected leaking, the U metal chips are able to open to air. A new oxidation treatment process was raised for a long time safe storage with concepts of drying under vacuum, evaporating the containing water and organic material with elevating temperature, and oxidizing the uranium metal chips at an appropriate high temperature under conditions of controlling the feeding rate of oxygen gas. In order to optimize the oxidation process the uranium metal chips were completely dried at higher temperature than $300^{\circ}C$ and tested for oxidation at various temperatures, which are $300^{\circ}C$, $400^{\circ}C$, and $500^{\circ}C$. When the oxidation temperature was $400^{\circ}C$, the oxidized sample for 7 hours showed a temperature rise of $60^{\circ}C$ in the self-ignition test. But the oxidized sample for 14 hours revealed a slight temperature rise of $7^{\circ}C$ representing a stable behavior in the self-ignition test. When the temperature was $500^{\circ}C$, the shorter oxidation for 7 hours appeared to be enough because the self-ignition test represented no temperature rise. By using several chemical analyses such as carbon content determination, X-ray deflection (XRD), Infrared spectra (IR) and Thermal gravimetric analysis (TGA) on the oxidation treated samples, the results of self-ignition test of new oxidation treatment process for U metal chip were interpreted and supported.

• 한국표면공학회지
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• 제38권3호
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• pp.126-135
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• 2005

SKD 11 steel has been widely used for tools, metallic mold and die for press working because of its favorable mechanical properties such as high toughness and creep strength as well as excellent oxidation resistance. The ion nitrided tool steel containing Mo results in improvement of corrosion resistance, strength at high temperature and pitting resistance, especially in $Cl^-$ contained environment. But the Mo addition causes a disadvantage such as lower oxidation resistance at elevated temperature. In this study, several effects of ion-disadvantage on the oxidation characteristics for SKD 11 steel with various oxidation temperature were investigated. SKD 11 steels were manufactured by using vacuum furnace and solutionized for 1 hr at $1,050^{\circ}C$. Steel surface was ion nitrided at $500^{\circ}C$ for 1 hr and 5 hr by ion nitriding equipment. ion nitrided specimen were investigated by SEM, OM and hardness tester. Oxidation was carried out by using muffle furnace in air at $500^{\circ}C,\;700^{\circ}C\;and\;900^{\circ}C$ for 1hr, respectively. Oxidation behavior of the ion nitrided specimen was investigated by SEM, EDX and surface roughness tester. The conclusions of this study are as follows: It was found that plasma nitriding for 5 hr at $500^{\circ}C$, compared with ion nitriding for 1 hr at $500^{\circ}C$, had a thick nitrided layer and produced a layer with good wear, corrosion resistance and hardness as nitriding time increased. Nitrided SKD 11 alloy for 1hr showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with nitrided SKD 11 alloy for 5 hr. The oxidation surface at $900^{\circ}C$ showed a good corrosion resistance.

• 한국재료학회지
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• 제3권4호
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• pp.403-409
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• 1993

본 논문에서는 Si(111)에 대한 건식산화와 어닐링에서 결함의 억제 또는 제거에 $NH_3$가 효과적임을 밝혔다. 산화방식은 건식산화(dry $O_2$ oxidation)및 $NH_3$산화($NH_3$ added in dry $O_2$oxidation)를 택하였고 $N_2$및 $NH_3N_2$분위기에서 어닐링 효과를 평가하였다. 건식산화에서는 발생되는 결함이 성장시간에 따라서 길이가 길어지며, $NH_3$산화에서는 결함이 발견되지 않았다. 또한 초기산화를 $NH_3$산화로 하고서 건식산화를 하였을 때 계면에서의 결함을 제거하는 효과가 있다. 건식산화 또는 $NH_3$산화를 한 후 이들 시료에 대하여 7.5% $NH_3N_2$분위로 어닐링하면OSF의 게터링(gettering)효과가 있었다. $NH_3$산화방식에서 7.5%$NH_3N_3$분위기로 어닐링했을때가 건식산화방식에 비하여 OSF의 길이가 20%정도 감소하였다. OSF의 모양은 pit형으로 (111)면에 대하여 (011)면 쪽으로 게터링이 일어났으며<110>방향으로 식각되는 성질이 있었다.

• 한국환경보건학회지
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• 제26권4호
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• pp.49-57
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• 2000

This study was carried out to find the optimal condition to treat refractory organic matter which can’t treat clearly with biological treatment and to find the optimal division dosage and division dose timing in the modification of Fenton oxidation which is used resolve the problem that hydrogen peroxide is too expensive. The results are following; 1. The highest TOC removal efficiency was 41% and color removal efficiency was 64% when the dilution magnitude of leachate is fold. This suggests that dilution is efficiency when high concentration of leachate is treated. 2. The removal efficiency of TOC and color increased up to the molar ratio between ferrate and hydrogen peroxide was 1:1. However above that ratio, removal efficiency hardly increased. The highest removal efficiency of TOC and color were 38% and 71% when the mole ratio of ferrate to hydrogen peroxide was 1.5:1. 3. When the mole ratio between ferrate and hydrogen peroxide was fixed, the removal efficiency of TOC and color increased as the dosage of hydrogen peroxide increased. 4. pH of samples were adjusted at pH 3, 5, 7, 9, 11. After oxidation reaction, pH of samples were dropped to 2.59, 2.54, 5.34, 6.36 and 9.68. The highest color removal efficiency was 75.7% when initial pH was at pH 7. 5. The removal of TOC and color was ended within 10. min. and the removal efficiency increased logarithmically within 10min. However after 10 min., the removal efficiency of hardly increased. 6. The color removal efficiency was higher with modification of fentone oxidation than that with fentone oxidation by 5%. Optimal division dosage ratio was 1:1 and optimal dose timing ratio was 2:1. However the TOC removal efficiency was not higher with modification of Fenton oxidation than that with Fenton oxidation.7. The CO $D_{Mn}$ /BO $D_{5}$ Ratio decreased with the time went by. It meant bioresolution increased as time went by. However, after 15 min., the CO $D_{Mn}$ /BO $D_{5}$ Ratio did not decrease any more. 8. In the case of $H_2O$$_2$ Divisiom Dose experiment, the increase of bioresolution was highest at the $H_2O$$_2$ Division dosage Ratio of 3:7.3:7.

• 한국환경기술학회지
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• 제19권6호
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• pp.556-562
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• 2018

현재 하수종말처리장은 질소와 인의 방류수 수질기준 강화로 생물학적 처리 후 약품주입으로 잔류인의 처리를 하고 있는 실정에서 방류수 수질기준은 확보가 가능하나, 약품주입량의 과다와 발생되는 슬러지의 증대 및 발생슬러지의 탈수효율 저하로 슬러지처리과정에서 또 다른 문제가 발생하여 처리에 대한 신뢰성이 결여되어 있는 실정이다. 그러므로 본 연구는 기존 하수종말처리장에서 발생하고 있는 문제에 대하여 최소의 반응시간과 슬러지 발생량의 최소화를 토대로 생물학적 고도처리를 적용한 하수처리장에서 방류수 수질기준의 강화에 따라 생물학적 처리로 확보하기 어려운 안정적 처리방식과 처리수질변동에 대한 적응 및 질소와 인의 처리기준을 맞추기 위하여 기존 하수처리 방식에 Electro Coagulation and Oxidation system을 적용한 결과 다음과 같다. 1) Al-SUS(stainless steel)로 배치한 전극에서 반응시간대와 상관없이 $15mA/cm^2$의 전류밀도에서 BOD, TN 및 TP의 처리효율이 $5mA/cm^2$에서의 처리효율보다 높게 나타났으나, 전류밀도 $10mA/cm^2$ 이상만을 유지하여도 TP의 경우 대부분 0.1 mg/L 정도로 처리가 가능하며, 특히, 반응시간을 10 min으로 유지할 경우 TP농도는 전류밀도와 상관없이 0.06 mg/L 이하로 방류수 수질기준 0.1 mg/L 이하를 유지할 수 있었다. 2) TP농도의 변화는 전류밀도의 변화에 영향을 크게 받지 않으며, 오히려 반응시간에 따라 처리수의 농도가 변화하는 것으로 전기응집반응의 경우 수초~수분이 요구되나 전기산화와 동시에 반응이 일어나야 하므로 적절한 전기응집산화의 반응시간은 10 min 이상이 요구되는 것으로 연구되었다. 3) 결과적으로 본 연구에서 생활하수의 TN 및 TP처리를 위한 전기응집산화공정의 경제적인 전류밀도는 $15mA/cm^2$이하, 반응시간은 10 min을 유지하는 것이 적절한 것으로 연구되었다.

• 한국자기학회지
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• 제12권3호
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• pp.99-102
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• 2002

기존 절연막보다 균일한 AlO 절연막을 형성하기 위해 플라즈마 산화법을 이용하여 이중 연속 절연막을 형성한 TMR소자를 제작하였다. 10 $\AA$의 Al 하부 절연막의 산화시간을 10sec로 우선 완성하고 그 위에 13 $\AA$의 Al을 성막하고 50, 80, 120sec간 산화시켜 완성한 절연막의 특성을 알아본 결과 산화시간이 증가할수록 전기저항은 500 $\Omega$에서 2000 $\Omega$까지 크게 변화하며 80sec 에서 가장 작았고, MR비는 27~31 %로 큰 변화가 없었으나, 단일산화 절연막을 가진 시편(24%)보다는 모두 높은 자기저항비를 보였다. I-V측정을 통해 간접적으로 유효 장벽 높이와 장벽 폭을 계산한 결과 장벽 높이는 1.3~1.8eV로 터널링 장벽으로서 충분한 크기를 보였으며 장벽 폭의 경우에는 15.0 $\AA$ 이하로 실제 물리적으로 측정한 값보다 작음을 알 수 있었다. 이는 Al금속이 완전히 안정한 A1$_2$O$_3$로 산화되지 않았기 때문으로 생각되었으며, 그럼에도 불구하고 단일 AlO 절연막 시편보다는 균일하고 치밀한 절연막을 형성하였음을 확인하였다. 이러한 결과는 이중절연층 산화공정이 기존 공정보다 절연장벽을 우수하게 하여 MR비를 향상시키고 기준저항을 조절하는데 유리한 공정임을 의미하였다.

• 한국자기학회지
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• 제14권3호
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• pp.99-104
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• 2004

자기 터널 접합(Magnetic Tunnel Junction, MTJ)의 플라즈마 산화시간과 열처리 온도에 따른 자기저항(Tunneling Magnetoresistance, TMR) 온도의존특성을 연구하였다. 플라즈마 산화시간을 30$_{s}$ 70$_{s}$ 까지 10$_{s}$ 간격으로 변화시켜 측정한 결과, 산화시간 50초에서 상온에서 25.3%의 가장 높은 TMR 비를 얻었다. 스핀 분극도 $P_{0}$ 스핀파 지수(spin wave parameter) $\alpha$를 구한 결과, 산화시간 50$_{s}$ 에서 40.3%의 가장 높은 스핀 분극도와 가장 낮은 온도 의존 특성인 (10$\pm$4.742)${\times}$$10^{-6}$ $K^{－1.5}$스핀파 지수(spin wave parameter) $\alpha$값을 얻었다. 그리고 온도별 열처리 결과 175$^{\circ}C$에서 TMR비가 25.3%에서 27.5%까지 증가하였으며 스핀파 지수는 (10$\pm$0.719)${\times}$$10^{-6}$ K $^{－1.5}$ 까지 감소하여 온도의존도가 감소하였다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.459-463
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• 2012

N-hydroxyphthalimide (NHPI) and copper chloride ($CuCl_2$) were first utilized for aerobic oxidation of ${\alpha}$-isophorone (${\alpha}$-IP) to ketoisophorone (KIP) and the effects of co-catalysts, temperature, reaction time, solvent, amount of $CuCl_2$ and pressure of oxygen were investigated extensively. NHPI/$CuCl_2$ turned out to be highly efficient to this oxidation with up to 91.3% conversion and 81.0% selectivity under mild conditions. And various hydrocarbons including benzylic compounds, cycloalkene and its derivatives were also oxidized smoothly under optimized conditions. Moreover, the possible reaction mechanism was proposed and verified by FT-IR spectra.

• 연구논문집
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• 통권34호
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• pp.139-146
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• 2004

In this study, effect of temperature and time on melt-out of 25wt% Al-alloyed ductile iron has been investigated. The oxidation tests were carried out in a tube furnace at $800^\circC$, $930^\circC$, and $1000^\circC$ for lh, 5h, 10h, 50h. The microstructure, microhardness, and $Al_2O_3$ layer of oxidation-treated 25wt% Al-alloyed ductile iron samples (10 x 10 x 10 mm) were investigated. Phase identification was performed by X-ray diffraction(XRD) and EDS. The oxidation-treated 25wt% Al-alloyed ductile iron samples at $930^\circC$ for lh, 5h, 10h and KS GCD 500 were used for melt-out test in an Al alloy melt. The melt-out test results showed that oxidation tested sample at $930^\circC$ for 5h which on the whole forms $2-3\mum$ $Al_2O_3$ layer showed lowest melt-out depth. It was observed showed that appropriate Al203 layer can affect melt-out behaviors.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.378-385
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• 2018

An experimental study was conducted to investigate behavior of surface oxidation with steel type. The excess entalphy combustion in porous media system was applied to implement the direct radiation heating system. The surface oxidation thickness (SOT) in fuel-lean condition was thicker than the SOT in fuel-rich. Also, the SOT was increased by increasing residence time. Detailed explanations were given by SEM and EDS analysis.