• 한국환경보건학회지
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• 제32권3호
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• pp.207-214
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• 2006

This study was designed to assess the level of nitrogen dioxide from several microenvironments including inside the home, outdoors near the home, inside the school, outdoors near the school, and on the road for 42 primary schoolchildren during the month of December 2002 in Seoul, Korea. The average personal, indoor, outdoor $NO_2$ levels, and indoor/outdoor ratio were 45.08 ppb, 27.89 ppb, 30.96 ppb, and 0.89, respectively. The indoor $NO_2$ concentrations were significantly associated with the presence of a smoker with a gas stove. The estimated personal $NO_2$ exposure using time-weighted average equation of $34.64{\pm}5.29$ ppb was significantly lower than the measured personal exposure of $45.08{\pm}5.50$ ppb. Our results indicate that indoor $NO_2$ levels were associated with the presence of a smoker and a gas stove. Moreover, personal $NO_2$ exposure with a gas stove in the house was significantly higher than those without a gas stove.

• 센서학회지
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• 제28권4호
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• pp.225-230
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• 2019

$Au@TiO_2$ core-shell decorated rGO nanocomposite (NC) was prepared using a simple solvothermal method followed by heat treatment for gas sensor application. The crystal structure and morphology of the composites were characterized by X-ray powder diffraction and transmission electron microscopy, respectively. The $NO_2$ sensing response of the $Au@TiO_2/rGO$ NC was tested at operating temperatures from $250^{\circ}C$ to $500^{\circ}C$, and was compared with those of the bare rGO and $Au@TiO_2$ core-shell NPs. The $Au@TiO_2/rGO$ NC-based sensor showed a far higher response than the rGO or $Au@TiO_2$ core-shell based sensors, with the maximum response detected when the operating temperature was $400^{\circ}C$. This improved response was due to the high rGO gas absorption capability for $NO_2$ gas and the catalytic effect of $Au@TiO_2$ core-shell NPs in oxidizing $NO_2$ to $NO_3$.

• 한국응용과학기술학회지
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• 제34권2호
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• pp.367-375
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• 2017

본 연구에서는 배가스 내 존재하는 오염물질인 NO의 처리효율을 증대시키기 위하여 NO 산화공정을 연구하였으며, 강력한 산화력의 건식산화제를 제조하는 방법으로 $H_2O_2$ 촉매분해가 도입되었다. $H_2O_2$ 분해공정 상에서 적용 가능한 $K-Mn/Fe_2O_3$ 불균일계 촉매가 제조되었으며, 이들이 가지는 물리화학적 특성이 $H_2O_2$ 분해반응에 미치는 영향이 조사되었다. 제조된 건식산화제는 NO가 포함된 모사 배가스를 처리하기 위한 NO 산화공정에 적용되었으며, 다양한 모사 배가스의 유량(5, 10, 20 L/min)에서 약 100% 가까운 NO 전환율을 확인 하였다.

• 한국세라믹학회지
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• 제39권10호
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• pp.988-993
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• 2002

Lanthanum Stannate Pyrochlore($La_2Sn_2O_7$) 촉매를 이용하여 $NO_x$ 제거를 위한 전기화학 촉매 셀을 제조하였다. 촉매전극은 수열합성법을 통해 합성한 $La_2Sn_2O_7$ 분말과 안정화 지르코니아(YSZ) 분말을 혼합하여 촉매층 페이스트를 제조한 후 이를 YSZ 디스크 고체전해질 위에 스크린프린팅하여 후막을 도포하였다. 위와 같이 제조한 전기화학 셀의 $NO_x$ 분해 실험은 galvanostat을 이용하여 셀에 일정한 전류를 인가하고 700${\circ}C$에서 NO 0.1%와 산소 2%의 반응가스에 대한 분해 정도를 gas chromatography와 NOx analyzer를 이용하여 측정을 하였다. 촉매 전극의 두께와 소성 온도에 따른 촉매전극의 미세구조가 $NO_x$ 분해에 미치는 영향과 전류량(0.05∼0.6A)에 따른 $NO_x$ 분해율을 측정하였다.

• 대한기계학회논문집B
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• 제32권8호
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• pp.597-603
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• 2008

The catalyzed diesel particulate filter (CDPF) is widely used for collecting soot from the exhaust gas of diesel engine. However, the CDPF need being regenerated after the soot accumulation. It is important to know characteristics of regeneration for CDPF with variation of exhaust gas temperature and composition. This study presents characteristics of regeneration according to variable exhaust gas composition. Furthermore, the experiment were performed variable gas temperature of CDPF inlet gas at each exhaust gas composition. Test-rig is used to control at each in let gas temperature and composition during regeneration of CDPF. Reaction intensity($I_c$) is used to compare with each result. Experimental results indicated that increased concentration of $NO_x$ and $O_2$ lead to regenerate more greatly. Also, higher temperature of exhaust gas leads to make CDPF cleaner.

• 대한환경공학회지
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• 제29권1호
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• pp.62-67
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• 2007

본 연구의 목적은 액상 균일질 촉매를 이용하여 연소가스 중에 포함되어 있는 $SO_2/NO$의 동시제거 기술 개발에 있다. 연구는 bench scale/소규모 pilot scale에서 이루어졌으며 연구 결과는 다음과 같다. 1) $SO_2$는 실험조건에 상관없이 높은 제거효율을 가지는 것으로 확인되었다. 그러나 NO의 경우 충진층 높이가 증가할수록, 농도가 낮을수록, 촉매 분사량이 증가할수록 제거효율이 증가하는 것으로 나타났다. 2) Fe(II)-EDTA를 이용한 $SO_2/NO$ 동시처리 기술 개발을 위한 최적의 설계 인자는 충진 높이 =0.5 m, 액체-기체비 = 20 $L/m^3$, 반응기 단수=3단, 반응기 단면적 = 0.025 $m^2$로 결정하였다. 3) 연구 결과를 기초로 $SO_2/NO$의 동시처리 효율을 실험한 결과 각각 95%, 81% 이상 제거가 가능했다. 4) 높은 HTU는 NO의 제거에 있어 유리하지만 과도한 HTU는 스크러버의 운전효율을 감소시키므로 최적의 HTU를 결정하는 것이 필요하다.

• 한국재료학회지
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• 제20권11호
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• pp.623-627
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• 2010

Semiconducting metal oxides have been frequently used as gas sensing materials. While zinc oxide is a popular material for such applications, structures such as nanowires, nanorods and nanotubes, due to their large surface area, are natural candidates for use as gas sensors of higher sensitivity. The compound ZnO has been studied, due to its chemical and thermal stability, for use as an n-type semiconducting gas sensor. ZnO has a large exciton binding energy and a large bandgap energy at room temperature. Also, ZnO is sensitive to toxic and combustible gases. The NO gas properties of zinc oxide-single wall carbon nanotube (ZnO-SWCNT) composites were investigated. Fabrication includes the deposition of porous SWCNTs on thermally oxidized $SiO_2$ substrates followed by sputter deposition of Zn and thermal oxidation at $400^{\circ}C$ in oxygen. The Zn films were controlled to 50 nm thicknesses. The effects of microstructure and gas sensing properties were studied for process optimization through comparison of ZnO-SWCNT composites with ZnO film. The basic sensor response behavior to 10 ppm NO gas were checked at different operation temperatures in the range of $150-300^{\circ}C$. The highest sensor responses were observed at $300^{\circ}C$ in ZnO film and $250^{\circ}C$ in ZnO-SWCNT composites. The ZnO-SWCNT composite sensor showed a sensor response (~1300%) five times higher than that of pure ZnO thin film sensors at an operation temperature of $250^{\circ}C$.

• 한국자동차공학회논문집
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• 제23권5호
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• pp.515-523
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• 2015

In this paper, we fabricated and evaluated the gas sensor for the detection of CO gas and $NO_X$ gas among the vehicle exhaust emission gasses. The $SnO_2$ (tin dioxide) layer is used as the detection material, and the thin-film type and the nano-fiber type layers are deposited with various thicknesses using sputtering method and electro spinning method, respectively. The experiments are performed in the chamber where the gas concentration is controlled with mass flow controller. The fabricated devices are applied to the CO and $NO_X$ gas, where the device with the thinner $SnO_2$ layer shows better sensitivity. The nano-fiber has the larger surface area, and the shorter response time and recovery time are obtained. From the experimental results, both types of gas sensors successfully detect CO and $NO_X$ gases, which can be applied to measure those gases from the vehicle emissions.

• 한국재료학회지
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• 제23권12호
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• pp.667-671
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• 2013

We present an easy method of preparing two-dimensional (2D) periodic hollow tin oxide ($SnO_2$) hemisphere array gas sensors using polystyrene (PS) spheres as a template. The structures were fabricated by the sputter deposition of thin tin (Sn) metal over an array of PS spheres on a planar substrate followed by calcination at an elevated temperature to oxidize Sn to $SnO_2$ while removing the PS template cores. The $SnO_2$ hemisphere array structures were examined by scanning electron microscopy and X-ray diffraction. The structures were calcined at various temperatures and their sensing properties were examined with varying operation temperatures and concentrations of nitric oxide (NO) gas. Their gas-sensing properties were investigated by measuring the electrical resistances in air and the target gases. The measurements were conducted at different NO concentrations and substrate temperatures. A minimum detection limit of 30 ppb, showing a sensitivity of S = 1.6, was observed for NO gas at an operation temperature of $150^{\circ}C$ for a sample having an Sn metal layer thickness corresponding to 30 sec sputtering time and calcined at $600^{\circ}C$ for 2 hr in air. We proved that high porosity in a hollow $SnO_2$ hemisphere structure allows easy diffusion of the target gas molecules. The results confirm that a 2D hollow $SnO_2$ hemisphere array structure of micronmeter sizes can be a good structural morphology for high sensitivity gas sensors.

• 대한환경공학회지
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• 제27권3호
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• pp.330-336
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• 2005

본 연구에서는 촉매공정의 질소산화물 제거 성능을 향상시키기 위하여 배기가스에 오존을 주입하였다. 배기가스에 오존을 주입하면 배기가스에 포함되어 있는 NO의 일부가 $NO_2$로 빠르게 산화되며, NO와 $NO_2$ 혼합물은 촉매반응기에서 $N_2$로 환원된다. 오존의 발생을 위해 유전체 장벽 방전 반응기가 사용되었고 촉매로는 상용 $V_2O_5-WO_3/TiO_2$ 촉매가 사용되었다. 질소산화물의 환원제는 암모니아였다. 촉매반응기 전단의 $NO_2$ 함량은 오존 주입량에 의해 변화될 수 있었으며, $NO_2$ 함량 변화가 촉매의 질소산화물 저감성능에 미치는 영향에 대해 살펴보았다. $NO_2$ 함량이 촉매반응기의 성능에 미치는 영향은 다양한 조건에서 수행되었는데, 주요 변수로 선정한 것은 반응온도, 초기 $NO_x$ 농도, 암모니아 농도, 그리고 배기가스 유량이었다. 오존주입에 의한 $NO_2$ 함량 증가는 촉매공정의 질소산화물 제거 성능을 크게 향상시킬 수 있었으며, 이러한 성능 향상 효과는 반응온도가 낮을수록 두드러졌다. 본 연구의 오존 주입 방법은 기존 촉매 공정의 개선에 크게 유용할 것으로 판단된다.