• Journal of information and communication convergence engineering
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• 제2권1호
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• pp.22-25
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• 2004

A highly sensitive ammonia gas sensor using thick-film technology has been fabricated and examined. The sensing material of the gas sensor is FeOx-$WO_{3}-SnO_{2}$ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. A novel method for detecting ammonia gas quite selectively utilizing a sensor array consisting of an ammonia gas sensor and a compensation element has been proposed and developed. The compensation element is a Pt-doped $WO_{3}-SnO_{2}$gas sensor which shows opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array having two sensing elements.

• Journal of Biosystems Engineering
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• 제23권4호
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• pp.359-364
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• 1998

A PC based measurement system was developed and it consisted of ammonia sensor(TS-1000), AMP & MUX Board, A/D Converter, and personal computer. The results obtained from the study are summarized as follows : 1. The relationship of outputs(V) of ammonia sensor(AS) and concentrations(ppm) of ammonia gas was analyzed by the linear regression analysis and the output values were very accurate when compared with standard ammonia gas. 2. The test results showed that the performance of ammonia gas sensor was not 31B3c1e4 by temperatures and humidities 3. The developed ammonia gas measurement system was proved to be practically uesful for measuring concentrations of ammonia gas in pig housing.

• 센서학회지
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• 제6권6호
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• pp.445-450
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• 1997

후막형 암모니아 가스센서를 제조하여 가스 감지특성을 조사하였다. 저농도의 암모니아 가스에 감도가 우수한 산화물 반도체 감지물질은 $FeO_{x}-WO_{3}-SnO_{2}$ 이었으며 100 ppm 이하의 암모니아 가스에 노출될 때 감지막의 저항이 증가하는 특이한 경향을 나타내었다. 반면 암모니아 외의 일반적인 환원성 가스에 노출될 때는 저항이 감소하는 경향을 보였다. 이러한 암모니아 가스 감지소자와 감지물질이 Pt-doped $WO_{3}-SnO_{2}$ 로 구성된 보상소자를 결합하여 센서어레이를 제조하였으며 그 특성을 조사하였다. 보상소자는 암모니아 가스와 일반적인 환원성 가스모두에 의해 저항이 감소하는 경향이 있다. 센서 어레이는 감지소자와 보상소자를 하나의 기판위에 형성하여 제조되었으며 우수한 선택성을 얻을 수 있었다. 이러한 개념의 센서어레이를 이용하면 가스센서의 선택성 향상을 기할 수 있음을 확인할 수 있었다.

• 센서학회지
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• 제25권6호
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• pp.423-430
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• 2016

This study used a single metal oxide semiconductor (MOS) sensor to classify the major odorous gases hydrogen sulfide ($H_2S$), ammonia ($NH_3$) and toluene ($C_6H_5CH_3$). In order to classify these odorous substances, the voltage on the MOS sensor heater was gradually reduced in 0.5 V steps 5.0 V to examine the changes to the response by the cooling effect on the sensor as the voltage decreased. The hydrogen sulfide gas showed the highest sensitivity compared to odorless air under approximately 2.5 V and the ammonia and toluene gases showed the highest sensitivity under approximately 5.0 V. In other words, the hydrogen sulfide gas reacted better in the low temperature range of the MOS sensor, and the ammonia and toluene gases reacted better in the high-temperature range. In order to analyze the response characteristics of the MOS sensor by temperature in a pattern, a two-dimensional (2D) x-y pattern analysis was introduced to clearly classify the hydrogen sulfide, ammonia, and toluene gases. The hydrogen sulfide gas was identified by a straight line with a slope of 1.73, whereas the ammonia gas had a slope of 0.05 and the toluene gas had a slope of 0.52. Therefore, the 2D x-y pattern analysis is suggested as a new way to classify these odorous substances.

• 센서학회지
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• 제26권2호
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• pp.96-100
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• 2017

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively studied as the active material in ammonia gas sensor because of its fast response time, high conductivity and environmental stability. It is well known that a post annealing process for organic devices based on PEDOT:PSS significantly increases the device performance. In this study, we propose the solvent annealing of PEDOT:PSS and investigated its effects. As a results, post solvent annealing on PEDOT:PSS lead to the surface chemical and physical properties change. These changes result in improved conductivity of the PEDOT:PSS. In additional, ammonia sensitivity of solvent annealed PEDOT:PSS become higher than pristine polymer film. The enhancement is mainly caused by the depletion of gas barrier PSS and structural re-forming PEDOT networks. We believe that the post solvent annealing is a promising method to achieve highly sensitivity PEDOT:PSS films for applications in efficient, low-cost and flexible ammonia gas sensor.

• Carbon letters
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• 제13권2호
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• pp.88-93
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• 2012

Polypyrrole (PPy)/multi-walled carbon nanotubes (MWCNTs) composites were prepared by in situ polymerization of pyrrole on the surface of MWCNTs templates to improve the ammonia gas sensing properties. PPy morphologies, formed on the surface of MWCNTs, were investigated by field emission scanning electron microscopy. The thermal stabilities of the PPy/MWCNTs composites were improved as the content of MWCNTs increased due to the higher thermal stability of the MWCNTs. PPy/MWCNTs composites showed synergistic effects in improving the ammonia gas sensing properties, attributed to the combination of efficient electron transfer between PPy/MWCNTs composites and ammonia gas, and the reproducible electrical resistance variation on PPy during the gas sensing process.

• 한국재료학회지
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• 제33권5호
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• pp.195-204
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• 2023

Micro-electronic gas sensor devices were developed for the detection of carbon monoxide (CO), nitrogen oxides (NO_x), ammonia (NH₃), and formaldehyde (HCHO), as well as binary mixed-gas systems. Four gas sensing materials for different target gases, Pd-SnO₂ for CO, In₂O₃ for NO_x, Ru-WO₃ for NH₃, and SnO₂-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were then fabricated using a micro sensor platform. The gas sensing behavior and sensor response to the gas mixture were examined for six mixed gas systems using the experimental data in MEMS gas sensor arrays in sole gases and their mixtures. The gas sensing behavior with the mixed gas system suggests that specific adsorption and selective activation of the adsorption sites might occur in gas mixtures, and allow selectivity for the adsorption of a particular gas. The careful pattern recognition of sensing data obtained by the sensor array made it possible to distinguish a gas species from a gas mixture and to measure its concentration.

• Journal of Biosystems Engineering
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• 제28권5호
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• pp.457-464
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• 2003

The purpose of this study was to develop a pilot scale bio-filter system removing ammonia gas with microorganisms. The system consisted of chaff(filter medium), a blower, a temperature sensor, a moisture sensor, a solenoid valve, and a heating system. Temperature and moisture contents were controlled via a PC to provide the microorganisms with proper environment. The microorganisms used in this study were Bacillius. coagulans NLRI T-6 and Pseudononas. putida NLRI S-21 of bacilli. Performance tests were performed to evaluate gas removal rate during 20 days. The result was shown that the removal rate was high in early days and gradually dropped below 90% without injecting the microbes. However, it was shown that when injecting the microbes, the removal rate was almost 100% and pH value was maintained at between 7 and 9 during the whole twenty-day period.

• 센서학회지
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• 제8권1호
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• pp.24-31
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• 1999

감도가 우수하고 동작온도가 낮으며 반응속도가 빠른 암모니아 가스 센서를 제작하기 위해 ZnO에 촉매불순물 $MoO_3$의 첨가비와 박막 성장분위기 가스를 변화시키면서 RF 마그네트론 스펏터링 방법으로 박막을 성장하였다. 전기적 안정성을 향상시키기 위해 성장된 박막들을 aging 하여 센서를 제작한 후 암모니아 가스의 검지 특성을 조사하였다. 촉매불순물을 첨가하거나 산소분위기에서 성장된 박막의 경우 감도가 향상되었으며, 이는 표면 캐리어 농도와 전자이동도의 증가를 나타냈다. ZnO에 $MoO_3$를 무게비로 0.875 wt.% 첨가한 박막으로 제작한 센서가 160 ppm의 암모니아 가스 농도와 $300^{\circ}C$의 동작온도에서 70정도의 최대감도를 보였다. 산소분위기에서 $330^{\circ}C$로 72시간 동안 aging한 박막으로 만든 센서는 감도가 57정도로 감소하였으나, 센서의 동작온도가 $250^{\circ}C$로 낮아졌고, 선형성이 좋았으며 더 안정된 특성을 나타냈다.

• 한국재료학회지
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• 제34권5호
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• pp.235-241
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• 2024

Gas identification techniques using pattern recognition methods were developed from four micro-electronic gas sensors for noxious gas mixture analysis. The target gases for the air quality monitoring inside vehicles were two exhaust gases, carbon monoxide (CO) and nitrogen oxides (NO_x), and two odor gases, ammonia (NH₃) and formaldehyde (HCHO). Four MEMS gas sensors with sensing materials of Pd-SnO₂ for CO, In₂O₃ for NO_X, Ru-WO₃ for NH₃, and hybridized SnO₂-ZnO material for HCHO were fabricated. In six binary mixed gas systems with oxidizing and reducing gases, the gas sensing behaviors and the sensor responses of these methods were examined for the discrimination of gas species. The gas sensitivity data was extracted and their patterns were determined using principal component analysis (PCA) techniques. The PCA plot results showed good separation among the mixed gas systems, suggesting that the gas mixture tests for noxious gases and their mixtures could be well classified and discriminated changes.