• 한국가스학회지
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• 제21권2호
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• pp.41-49
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• 2017

최근 화학물질을 사용하는 시설이 증가하면서 취급양도 급속하게 증가하고 있다. 그러나 화학물질 누출사고는 꾸준히 발생되고 있으며 때에 따라 다량의 화학물질이 누출되는 경우에는 큰 피해로 이어질 가능성이 크다. 이러한 산업단지에는 수많은 센서로부터 얻는 정보를 이용해 누출 발생지역을 감지 감시하고 있으며, 기존의 고정식 센서를 로봇이나 드론에 적용하여 산업현장에 이용되고 있다. 이에 따라 화학물질을 취급하는 공정의 누출조건, 환경조건을 반영한 다양한 누출 시나리오를 토대로 빠른 감지와 대응을 위해 경계면의 센서 배치 방안을 제시할 필요가 있다. 따라서 본 연구에서는 화학물질이 누출되는 경우에 대해 COMSOL을 사용하여 주요 파라미터를 적용, 실질적인 사고 시나리오를 해석하였다. 그리고 사고 시나리오를 바탕으로 센서의 감지 확률, 감지시간과 감지시나리오 수의 각 항목마다 중요도를 부여하여 이동식 센서의 위치별 속도가 산출되도록 목적함수를 선정하였다. 또한 예상치 못한 누출사고에 대해 신뢰성 분석을 통해 제안방법의 타당성을 확인하였다. 이상의 결과로부터 추후 적용될 이동식 센서의 농도 데이터를 기반으로 누출원의 역추적에도 도움을 줄 수 있을 것으로 기대한다.

• Transactions on Electrical and Electronic Materials
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• 제16권6호
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• pp.334-337
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• 2015

Pure ZnO, ZnO nanowires doped with 3 wt.% Ga (3GZO) and doped with 3 wt.% Ag (3SZO) were grown by a hot-walled pulse laser deposition (HW-PLD) technique. The optical and chemical properties of Ga and Ag doped nanowires was analyzed. Nanowires were determined to be under 200 nm in diameter and several μm in length. Change of significant resistance was observed and the gas detection sensitivities of ZnO, 3GZO and 3SZO nanawires were compared. The sensitivities of ZnO, 3GZO, and 3SZO nanowire sensors were measured at 300℃ for 1 ppm of ethanol gas at 97%, 48%, and 203%, respectively.

• 한국세라믹학회지
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• 제36권5호
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• pp.465-470
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• 1999

Sensing properties of $\alpha$-Fe2O3 thin film to reducing gases such as CHx and CO were systematically examined after deposition on Al2O3 substrate by PECVD(Plasma Enhanced Chemical Vapor Deposition)technique. Microstructure of deposited $\alpha$-Fe2O3 thin film showed the porous island structure. This specimen was annealed at 450, 550, $650^{\circ}C$ to enhance the gas sensing properties and investigated in terms of CO and C4H10 concentration from 500ppm to 3,000 ppm at operating temperature of 35$0^{\circ}C$ The gas sensitivity(%) to C4H10 measured at the operating temperature of 35$0^{\circ}C$ was 98.24 (highest sensitivity) 69.51 to CO and 2% to CH4 respectviely.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.358-359
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• 2006

Ru-C nano-composite films were prepared by MOCVD, and their microstructures and their electrode properties for oxygen gas sensors were investigated. Deposited films contained Ru particles of 5-20 nm in diameter dispersed in amorphous C matrix. The AC conductivities associating to the interface charge transfer between Ru-C composite electrode and YSZ electrolyte were 100-1000 times higher than that of conventional paste-Pt electrodes. The emf values of the oxygen gas concentration cell constructed from the nano-composite electrodes and YSZ electrolyte showed the Nernstian theoretical values at low temperatures around 500 K. The response time of the concentration cell was 900 s at 500 K.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.417-428
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• 2018

In this study, we fabricated hierarchically self-assembled thin films composed of graphene oxide (GO) sheets and gold nanoparticles (Au NPs) using the Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques and investigated their gas-sensing performance. First, a thermally oxidized silicon wafer ($Si/SiO_2$) was hydrophobized by depositing the LB films of cadmium arachidate. Thin films of ligand-capped Au NPs and GO sheets of the appropriate size were then sequentially transferred onto the hydrophobic silicon wafer using the LB and the LS techniques, respectively. Several different films were prepared by varying the ligand type, film composition, and surface pressure of the spread monolayer at the air/water interface. Their structures were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and their gas-sensing performance for $NH_3$ and $CO_2$ was assessed. The thin films of dodecanethiol-capped Au NPs and medium-sized GO sheets had a better hierarchical structure with higher uniformity and exhibited better gas-sensing performance.

• 반도체디스플레이기술학회지
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• 제11권1호
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• pp.55-59
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• 2012

NOx is one of the toxin gases, which is mainly causing the optic-chemical smog phenomena, and decreasing in the function of nose and taste. Especially, NO is easily reacting with $O_3$, and then becoming the $NO_2$. $NO_2$ is mainly causing the acidulation rain. So, we should develop the NOx gas sensing system to detect NOx gas. In this paper, we present the microstructure and the NOx gas detecting properties of the nitrocellulose/MWCNT thin film coated by the air-spray on the glass substrate. The nitrocellulose/MWCNT-based gas sensors have been studied detecting NOx molecules of a ppm-level at the temperature range of $30{\sim}120^{\circ}C$. The resistance of the sensors decreases when the sensors are exposed to NOx gas. As a results, we obtained the nitrocellulose/MWCNT sensors with the sensitivity of 0.6%/sec under the 0.8 ppm of NOx gas concetration. Also, we get the activation energy of 0.202eV from the sensor for the 0.3 ppm of NOx gas concentration.

• 센서학회지
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• 제24권4호
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• pp.258-263
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• 2015

In order to prevent drink-driving by detecting concentration of alcohol from driver's exhale breath, twenty chemical sensors fabricated. The one of purposes for sensor array which consists of those sensors is to discriminate between target gas(alcohol) and interference gases($CH_3CH_2OH$, CO, NOx, Toluene, and Xylene). Wilks's lambda was presented to achieve above purpose and optimal sensors were selected using the method. In this paper, step-wise sensor elimination based on Euclidean distance was investigated for selecting optimal sensors and compared with a result of Wilks's lambda method. The selectivity and sensitivity of sensor array were used for comparing performance of sensor array as a result of two methods. The data acquired from selected sensor were analyzed by pattern analysis methods, principal component analysis and Sammon's mapping to analyze cluster tendency in the low space (2D). The sensor array by stepwise sensor elimination method had a better sensitivity and selectivity compared to a result of Wilks's lambda method.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.137-137
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• 2003

Conducting PPy/PVA composite and pure PPy gas sensors were prepared by in-situ vaporstate polymerization method in a vaporization chamber under N2 condition, by exposing the pre-coated electrode with PVA/FeC13 to distilled pyrrole monomer. The various electrical sensing behaviors of both types of sensors were systematically investigated by a flow measuring system including mass flow controller (MFC) and bubbling bottle. The FT-Raman spectroscopy of vapor state polymerized PPy was identical to that of chemically polymerized PPy, confirming the same chemical structure. Both types of sensors had positive sensitivity when exposed to methanol gas. The sensitivity varied linearly with gas concentration in the range of 50ppm to 1059ppm. The detection limit of PPy/PVA sensor was believed to be as low as 10ppm. The sensitivity of PPy/PVA composite sensor was higher than that of pure PPy sensor. Both the response time and recovery time of PPy/PVA composite sensors were longer than those of pure PPy sensors. The thickness of the sensing film affected the sensitivity this way that the sensor having thinner film had higher sensitivity, indicating that the resistance of polymer film involved in the sensing behavior was bulk resistance rather than surface resistance. The reproducibility of PPy/PVA composite sensor was excellent during eight on-off cycles by switching between N2 and 3000ppm methanol gas. The sensitivity of PPy/PVA composite sensor was only maintained for two weeks, while the sensitivity of pure PPy sensor was maintained over two months.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2373-2379
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• 2023

In sodium systems, leakage is one of the safety concerns; it can cause chemical reactions, which may result in fires. There are contact and non-contact types of leak detectors, and the conventional method of non-contact type detection is by gas sampling. Because of the complexity of this method, there has always been a need for a simple gas sensor, and the resistive-type nanostructure ZnO sensor is a promising option with various advantages. In this study, a ZnO sensor was fabricated, and the concept was tested as a leak detector using a dedicated experiment facility. The experiment results showed distinctive changes in resistance with the presence of sodium aerosol under various conditions. Replacing the conventional gas sampling with the ZnO sensors is expected to enable identification of the leakage location if used as a point-wise instrumentation and to greatly reduce the total cost, making the system simple, light, and effective. For further study, more tests will be performed to evaluate the sensitivity of key parameters under various conditions.

• 한국가스학회지
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• 제15권6호
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• pp.8-13
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• 2011

유해 위험 요인이 있는 시설물의 안전에 대한 의식을 고취시키기 위해서는 현장 종사자뿐만 아니라 관리자와 경영자도 해당 시설물에 대한 모니터링이 가능해야 한다. 그러나 우리나라에 있는 대부분의 CNG충전소는 로컬 형식의 모니터링 시스템이 사용되고 있으며 이러한 점을 고려하여 웹상에서 운용할 수 있는 충전소 관리 시스템을 개발 하였다. 개발된 시스템은 U-GSMS(Ubiquitous Gas Safety Management System)라고 명명 하였다. U-GSMS는 크게 프로그램 부분과 하드웨어 부분으로 나눌 수 있다. 프로그램 부분은 안전과 운영을 관리 할 수 있는 시스템으로 구성하였으며 하드웨어 부분은 가스시설물에 적용할 수 있는 센서, 센서간의 통신 그리고 센서와 기기 간의 통신을 위하여 USN(Ubiquitous Sensor Network)기술을 적용하여 무선 통신 시스템을 구축하였다. 이 논문에서는 주로 U-GSMS 중 프로그램에 관하여 기술하였다.