• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.106-111
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• 2005

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2-8wt.\% Y_{2}O_3$ ceramic coating during cyclic oxidation. $Al_{2}O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_{2}O_4 and Ni(Al,Cr)_{2}O_4$ during cyclic oxidation It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr,Al)_{2}O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• Korean Chemical Engineering Research
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• 제55권1호
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• pp.121-129
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• 2017

$TiO_2$, $Al_2O_3$, $ZrO_2$, $SiO_2$와 같은 다양한 담체에 습식함침법을 이용하여 Pd 기반 촉매를 제조하여 일산화탄소 존재하에 수소의 선택적 산화반응에 적용하였다. 제조된 촉매는 물리화학적 특성을 알아보기 위하여 XRD, $N_2$ 흡착, CO-, (CO+$H_2O$)-TPD, CO-TPR, XPS등의 특성분석을 수행하였다. CO-TPD와 (CO+$H_2O$)-TPD를 통해 $CO_2$ 탈착에 대한 $H_2O$의 영향을 알아보았으며 이러한 TPD 결과는 $H_2/CO$ 전환율과 상관관계가 있음을 확인하였다. 사용된 촉매 중에서 $Pd/ZrO_2$가 $H_2$ 전환율 측면에서 가장 활성이 좋은 것으로 나타났다. $H_2O$가 첨가된 선택적 $H_2$ 산화반응에서는 $H_2O$, CO, $H_2$가 경쟁흡착을 하였으며, 첨가된 $H_2O$가 CO 및 $H_2$의 반응을 촉진시켰다.

• 대한환경공학회지
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• 제27권2호
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• pp.184-190
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• 2005

하수 슬러지를 펜톤 산화공정으로 처리하는 새로운 VFAs 생산 공정을 연구하였다. 과산화수소와 촉매인 $Fe^{2+}$의 적정농도를 실험하고, 최적 반응온도 및 반응시간에 대한 기초 자료를 얻고자 하였다. 기존의 과산화수소를 액상산화제로 사용한 공정보다 저농도의 $Fe^{2+}$를 촉매로 사용하는 펜톤 산화공정으로 과산화수소의 사용량을 대폭 감소시키고도 VFAs 생성량이 4배 정도 증가하는 결과를 얻었다. 과산화수소와 $Fe^{2+}$의 적정 농도는 각각 0.62 M과 0.007M 이었다. VFAs 생성반응은 초기 1분 이내에서 빠르게 진행되었으며 생성된 VFAs의 일부가 초산과 $CO_2$로 분해되는 연속반응의 특성이 나타났다. 경제성을 감안하면 반응온도는 $25^{\circ}C$, 반응시간은 10분 정도가 적절한 반응조건으로 생각된다. 초기 pH $3{\sim}6.3$에서 VFAs의 생성에 미치는 pH의 영향은 관찰되지 않았다.

• 한국압력기기공학회 논문집
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• 제7권2호
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• pp.26-33
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• 2011

To evaluate steam oxidation behaviours of Alloy 617 and Haynes 230, oxidation test were performed at $900^{\circ}C$ in steam and $steam+20\;vol.-%\;H_2$ environments. Oxidation rate in steam condition was similar to that in air for Alloy 617, while it was slightly lower for Haynes 230. When hydrogen was added to steam, oxidation rate was enhanced. Isolated $MnTiO_3$ particle were formed on $Cr_2O_3$ oxide layer and sub layer $Cr_2O_3$ were formed in steam and $steam+20\;vol.-%\;H_2$ for Alloy 617. On the other hands, $MnCr_2O_3$ layer were formed on top of $Cr_2O_3$ oxide layer for Haynes 230. The extensive sub layer $Cr_2O_3$ formation was resulted from the oxygen inward diffusion in such environments. When hydrogen was added, the oxide morphology was changed from polygonal to platelet because of the accelerated diffusion of cations under the oxide layer. In addition, decarburized zone was extended as hydrogen participated into the reactions causing carbide dissolution.

• E2M - 전기 전자와 첨단 소재
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• 제8권3호
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• pp.352-356
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• 1995

Native oxide layer on MCT (HgCdTe) has been grown uniformly in H$\_$2/O$\_$2/ electrolyte through anodic oxidation method. It has been determined that anodic oxidation of HgCdTe in H$\_$2/O$\_$2/ electrolyte proceeds immediately with the input of constant currents without any induction time required for anodic oxideation in KOH electrolyte. Oxide layer with the resistivity of 2*10$\^$10/.ohm.cm and the refractive index of 2.1 suggested the possibility of well matching combination layer with ZnS for MCT MIS device. XPS results indicated that the major components of oxide layer grown in H202 solution is TeO$\_$2/ with the possibility of small amounts of CdTeO$\_$3/.

• 대한화학회지
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• 제34권6호
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• pp.534-538
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• 1990

H$_2$O을 용매로 하여 헤테로고리 염기인 이소퀴놀린과 CrO$_3$를 반응시켜 Cr(Ⅵ)화합물인 [$C_9H_7$NH]$_2Cr_2O_7$을 얻었다. 이 화합물은 비흡수성이면서 물에 잘 녹았다. 그리고 원소분석, 적외선 분광법으로 이 화합물의 구조가 [$C_9H_7$NH]$_2Cr_2O_7$임을 확인하였다. 또한, 이 화합물이 여러 가지 알코올을 알데히드나 케톤으로 전환시킬 수 있는 산화제로 작용하는가를 알아보기 위하여 알릴, 일차, 이차 알코올을 각각 산화반응에 이용한 결과 알코올들에 대해 효율적인 산화제로 작용하였다.

• Environmental Engineering Research
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• 제24권3호
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• pp.389-396
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• 2019

The electrical energy consumption (EEC) in removal of NO by a $UV/H_2O_2$ oxidation process was introduced and related to removal efficiency of this gas. The absorption-reaction of NO was conducted in a bubble column reactor in the presence of $SO_2$. The variation in NO removal efficiency was investigated for various process parameters including NO and $SO_2$ inlet concentrations, initial concentration of $H_2O_2$ solution and gas flow rate. EEC values were obtained in these different conditions. The removal efficiency was increased from about 22% to 54.7% when $H_2O_2$ concentration increased from 0.1 to 1.5 M, while EEC decreased by about 70%. However, further increase in $H_2O_2$ concentration, from 1.5 to 2, had no significant effect on NO absorption and EEC. An increase in NO inlet concentration, from 200 to 500 ppm, decreased its removal efficiency by about 10%. However, EEC increased from $2.9{\times}10^{-2}$ to $3.9{\times}10^{-2}kWh/m^3$. Results also revealed that the presence of $SO_2$ had negative effect on NO removal percentage and EEC values. Some experiments were conducted to investigate the effect of $H_2O_2$ solution pH. The changing of pH of oxidation-absorption medium in the ranges between 3 to 10, had positive and negative effects on removal efficiency depending on pH value.

• 한국표면공학회지
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• 제34권2호
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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.

• 한국수소및신에너지학회논문집
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• 제13권2호
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• pp.119-126
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• 2002

The methanol partial oxidation using commercial $CuO/ZnO/Al_2O_3$ catalysts in a plug flow reactor was studied in the temperature range of $200{\sim}250^{\circ}C$ at atmospheric pressure, It was achieved the high activities by Cu-based catalysts and the selectivity of $CO_2$/$H_2$ was 100% when $O_2$ was fully convened. The reactivity changes and their hysteresis with increasing/decreasing temperatures were observed due to the chemical state differences between the oxidation and the reduction on the Cu surface, It was suggested as the two-step reaction: the complete oxidation and the following steam reforming for methanol, which was indicated by the distributions of final products vs. the residence time. In addition, the complete oxidation step was shown to be extremely fast and the total reaction rate can be controlled by the steam reforming reaction.

• 공업화학
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• 제32권4호
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• pp.385-392
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• 2021

본 연구에서는 Co/CeO₂ 촉매 제조 시 코발트의 첨가 함량 및 세리아의 소성온도에 따른 물리·화학적 특성 및 일산화질소 산화 성능을 비교하였다. Co/CeO₂ 촉매의 구조적 특성은 XRD, BET 분석을 통하여 확인하였으며, 코발트 표면밀도에 따른 표면 결정 상태를 제안하였다. 또한, Raman, XPS 분석을 통하여 촉매의 산화가 및 산소 결합 상태를 확인하였으며, 일산화질소 산화 성능과의 관계를 제안하였다. H₂-TPR 분석을 통하여 촉매의 특성 변화에 따른 산소전달특성을 확인하였으며, 일산화질소 산화를 위한 촉매의 활성점(Co³⁺)을 제안하였다.