• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.622-626
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• 2010

Cu doped $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $500^{\circ}C$ in air, respectively. Structural properties of $SnO_2$ by X-ray diffraction showed (110), (101) and (211) dominant tetragonal phase. The effects of catalyst Cu in $SnO_2$-based gas sensors were investigated. Sensitivity of $SnO_2$:Cu sensors to 2,000 ppm $CO_2$ gas and 50 ppm $H_2S$ gas was investigated for various Cu concentration. The highest sensitivity to $CO_2$ gas and $H_2S$ gas of Cu doped $SnO_2$ gas sensors was observed at the 8 wt% and 12 wt% Cu concentration, respectively. The improved sensitivity in the Cu doped $SnO_2$ gas sensors was explained by decrease of electron depletion region in Cu and $SnO_2$ junction, and increase of reactive oxygen and surface area in the $SnO_2$.

• Journal of information and communication convergence engineering
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• 제7권1호
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• pp.72-77
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• 2009

Three different procedures for adding Pd compounds to $SnO_2$ particles have been investigated. These processes are: (1) coprecipitation; (2) dried powder impregnation; and (3) calcined powder impregnation. The microstructures of $SnO_2$ particles have been analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). In the coprecipitaion method, the process does not restrain the growth of $SnO_2$ particles and it forms huge agglomerates. In the dried powder impregnation method, the process restrains the growth of $SnO_2$ particles and the surfaces of the agglomerates have many minute pores. In the calcined powder impregnation method, the process restrains the growth of $SnO_2$ particles further and the agglomerates have a lot more minute pores. The sensitivity ($S=R_{air}/R_{gas}$) of the $SnO_2$ gas sensor made by the calcined powder impregnation process shows the highest value (S = 21.5 at 5350 ppm of $C_3H_8$) and the sensor also indicates the lowest operating temperature of around $410^{\circ}C$. It is believed that the best result is caused by the plenty of minute pores at the surface of the microstructure and by the catalyst Pd that is dispersed at the surface rather than the inside of the agglomerate. Schematic models of Pd distribution in and on the three different $SnO_2$ particles are presented.

• 공업화학
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• 제20권1호
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• pp.52-61
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• 2009

본 연구에서는 2액형 아크릴 우레탄 도료에 있어서 바인더로 사용되는 하이솔리드 아크릴 폴리올 수지를 개발함에 있어서 핵심요소인 반응 개시제로 TAPEH (t-amyl peroxy 2-ethyl hexanoate)를 선택하였다. 그리고 하이드록시 모노머는 Tone M100 (caprolactone acrylate), 4HBA (4-hydroxy butyl acrylate), 2HEMA (2-hydroxy ethyl methacrylate)를 사용하였다. 앞의 물질을 2액형 아크릴 우레탄 도료용으로 응용함에 있어서 적용성과 VOC 저감을 위하여, 알리파틱 폴리이소시아네이트 경화제 종류에 따른 반응성과 도막물성을 검토하였다. 또한 최근 주석계 촉매의 사용 억제에 따라 저독성 금속촉매와의 반응성 및 물성도 비교 시험하였다. 이상의 결과로부터 2액형 하이솔리드 폴리우레탄 수지 도료의 응용에 필요한 기초자료 확보로 도막물성과 작업성 개량 및 친환경 도료개발에 효과적으로 응용 할 수 있는 것을 검토하였다.

• 한국대기환경학회지
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• 제20권6호
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• pp.783-792
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• 2004

In this study, a thick-film semiconductor odor gas sensor for the detection of $CH_3$SH was developed using SnO$_2$ as the main substrate and was investigated in terms of its sensitivity and reaction time. In the process of manufacturing the sensor, Taguchi's design of experiment (DOE) was applied to analyze the effects of a variety of parameters, including the substrate, the additives and the fabrication conditions, systematically and effectively. Eight trials of experiments could be possible using the 27 orthogonal array for the seven factors and two levels of condition, which originally demands 128 trials of experiments without DOE. The additives of Sb$_2$O$_{5}$ and PdCl$_2$ with the H$_2$PtCl$_{6}$ ㆍ6$H_2O$ catalyst were appeared to be important factors to improve the sensitivity, and CuO, TiO$_2$, V$_2$O$_{5}$ and PdO were less important. In addition, TiO$_2$, V$_2$O$_{5}$ and PdO would improve the reaction time of a sensor, and CuO, Sb$_2$O$_{5}$, PdCl$_2$ and H$_2$PtCl$_{6}$ㆍ6$H_2O$ were negligible. Being evaluated simultaneously in terms of both sensitivity and reaction time, the sensor showed the higher performance with the addition of TiO$_2$ and PdO, but the opposite results with the addition of CuO, V$_2$O$_{5}$, Sb$_2$O$_{5}$ and PdCl$_2$. The amount of additives were superior in the case of 1% than 4%. H$_2$PtCl$_{6}$ㆍ6$H_2O$ would play an important role for the increase of sensor performance as a catalyst.nce as a catalyst.

• 조명전기설비학회논문지
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• 제16권6호
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• pp.130-136
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• 2002

본 논문은 비유전율이 100 이상으로 제작된 Ti-Si-Al형 세라믹 촉매 방전관에 전원 전압 4 ～6［kV］, 구동 주파수0.6～1.0［kHz］를 방전관 전극에 인가하여 오존 농도와 수율을 측정한 것이다. 측정 결과 구동 주파수 600［Hz］, 유량 2［1/min］, 동작 압력 1.6［atm］, 방전관 주위 온도 20［$^{\circ}C$］에서 산소 원료의 경우, 오존 발생 농도는 50～60［g/㎥］이었고, 오존 발생 수율은 180(g/kWh)로 나타났다. 그리고 반응기 내부 온도 또는 유입 가스 온도가 낮을수록 오존 수율은 상승하였다.

• 한국환경과학회지
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• 제14권2호
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• pp.221-230
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• 2005

Catalytic wet oxidation of trichloroethylene (TCE) in water has been conducted using $TiO_2-supported$ cobalt oxides at $36^{\circ}C$ with a weight hourly space velocity of $7,500\;h^{-1}.\;5\%\;CoO_x/TiO_2$, prepared by using an incipient wetness technique, might be the most promising catalyst for the wet oxidation although it exhibited a transient behavior in time on-stream activity. Not only could the bare support be inactive for the wet decomposition reaction, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. XPS spectra of both fresh and used Co surfaces gave different surface spectral features for each $CoO_x,\;Co\;2P_{3/2}$ binding energy for Co species in the fresh catalyst appeared at 781.3 eV, which is very similar to the chemical states of $CoTiO_x$ such as $CO_2TiO_4\;and\;CoTiO_3$. The used catalyst exhibited a 780.3-eV main peak with a satellite structure at 795.8 eV. Based on XPS spectra of reference Co compound, the TCE-exposed Co surfaces could be assigned to be in the form of mainly $Co_3O_4$. XRD patterns for $5\%\;CoO_x/TiO_2$ catalyst indicated that the phase structure of Co species in the catalyst even before reaction is quite comparable to the diffraction lines of external $Co_3O_4$ standard. A model structure of $CoO_x$ present predominantly on titania surfaces would be $Co_3O_4$, encapsulated in thin-film $CoTiO_x$ species consisting of $Co_2TiO_4$ and $CoTiO_3$, which may be active for the decomposition of TCE in a flow of water.

• 한국재료학회지
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• 제4권4호
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• pp.466-471
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• 1994

타이타니움이소프로폭사이드의 가수분해로 타이타니아 졸용액을 제조하고 그 특성을 조사하였다. 용매, 촉매 그리고 물의 양이 졸의 안정도에 미치는 영향을 조\ulcorner고, 서로 다른 온도에서 졸용액의 전단점도를 측정하여 그 각각의 gel time을 알아보았다. 안정한 조성의 졸용액을 이용하여 광학적으로 투명하고 균일한 타이타니아 박막을 제조할 수 있었다. 또한, 이차비선형 활성단을 도입한 후에도 좋은 박막을 제조할 수 있었다. 제조된 박막은 3~5kV, 50~$100^{\circ}C$ 온도범위에서 코로나 분극처리 하였다. 632.8nm He-Ne레이저를 이용하여 측정한 일차 전기 광학 상수, $r_{33}$는 1.5~5pm/V로서 경시 안정성을 나타내었다.

• 한국세라믹학회지
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• 제46권4호
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• pp.429-435
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• 2009

In this study, we investigated microstructure and the CO gas sensing properties of Ag-CuO-$SnO_2$ thin films prepared by co-evaporation and subsequently thermal oxidation at air atmosphere. The sensitivity of a Cu-Sn films, thermally oxidized at $600^{\circ}C$, is strongly affected by the amount of Cu. At Cu:7 wt%-Sn:93 wt%, the film exhibited a maximum sensitivity of ${\sim}2.3$ to CO gas of 1000 ppm at $300^{\circ}C$. In contrast, the sensitivity of a Sn-Ag film did not change significantly with the amount of Ag. An enhanced sensitivity of ${\sim}3.7$ was observed in the film with a composition of Ag:3 wt%-Cu:4 wt%-Sn:93 wt%, when thermally oxidized at $600^{\circ}C$. In addition, this thin film shows a response time of ${\sim}80$ sec and a recovery time of ${\sim}450$ sec to 1000 ppm CO gas. The results demonstrate that the CO sensitivity of the Ag-CuO-$SnO_2$ thin films may be closely associated with coexistence of $SnO_2$ and SnO phase, decrease in average particle size, and a porous microstructure. We also suggest that co-evaporation and followed by thermal oxidation is a very simple and effective method to prepare oxide gas sensor thin films.

• 한국재료학회지
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• 제20권5호
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• pp.235-240
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• 2010

We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of $500^{\circ}C$. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at $250^{\circ}C$ and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.

• 전기화학회지
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• 제10권4호
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• pp.279-282
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• 2007

개질기에서 생산된 수소를 연료전지용 연료로 사용할 때에는 개질수소가 포함하고 있는 일산화탄소가 막-전극접합체의 촉매를 피독시켜서 연료전지 성능이 크게 감소된다. 본 논문에서는 개질수소에 포함된 일산화탄소가 스퍼터링 공정으로 제조된 박막층에 의하여 개선된 막-전극접합체의 성능에 어떠한 영향을 미치는지 연구하였다. 실험결과 Pt와 Ru박막은 MEA의 단위전지 성능을 개선하였으며, 금속박막은 막-전극접합체의 일산화탄소에 대한 내구성을 증가시켰다. 산화전극으로의 공기주입 운전기법은 막-전극접합체의 일산화탄소에 대한 내구성을 증가시켰다. 게다가 Pt, Ru그리고 PtRu박막은 공기주입 운전에 영향을 주는 것으로 확인되었다.