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윤동현,권철한,홍형기,김승렬,이규정 ( Dong Hyun Yun,Chul Han Kwon,Hyung Ki Hong,Seung Ryeol Kim,Kyu Chung Lee ) 한국센서학회 1997 센서학회지 Vol.6 No.6
An ammonia gas sensor with high sensitivity using thick-film technology were fabricated and examined. The material for sensing the ammonia gas was the mixture of oxide semiconductor, FeO_x-WO₃-SnO₂. 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 were proposed and developed. The compensation element is a Pt-doped WO₃-SnO₂ gas sensor which shows opposite direction of resistance change in comparison with that of the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array having two sensing elements.
김승렬,운동현,홍형기,권철한,이규정 ( Seung Ryeol Kim,Dong Hyun Yun,Hyung Ki Hong,Chul Han Kwon,Kyu Chung Lee ) 한국센서학회 1997 센서학회지 Vol.6 No.6
The thick films of oxide semiconductors such as WO₃, SnO₂ and ZnO for the NO₂ detection of sub-ppm range have been prepared and their characteristics were investigated. It is showed that the optimum operating temperatures of the sensors are 300℃ and 220∼260℃ for WO₃-based and SnO₂-based thick films, and ZnO-based thick films, respectively. Since the resistance of ZnO-based thick films are extremely high($gt;l0^6Ω), the signal to noise ratio was comparatively low. In order to determine the selectivity, the films are exposed to the interfering gases such as ozone, ammonia, methane and the mixture of carbon monoxide and propane. WO₃-ZnO(3 wt.%) and SnO₂-WO₃(3 wt.%) thick film sensors show high sensitivity, good selectivity, excellent reproducibility and the linearity of NO₂ concentration versus sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the detection of NO₂ in sub-ppm range.
CO/HC 가스 인식을 위한 소형 전자코 시스템의 제작 및 특성
홍형기,권철한,윤동현,김승렬,이규정,김인수,성영권 ( Hyung Ki Hong,Chul Han Kwon,Dong Hyun Yun,Seung Ryeol Kim,Kyu Chung Lee,In Soo Kim,Yung Kwon Sung ) 한국센서학회 1997 센서학회지 Vol.6 No.6
system has been fabricated and characterized using an oxide semiconductor gas sensor array and pattern recognition techniques such as principal component analysis and back-propagation artificial neural network. The sensor array consists of six thick-film gas sensors whose sensing layers are Pd-doped WO₃, Pt-doped SnO₂, TiO₂-Sb₂O_5$gt;-Pd-doped SnO₂, TiO₂-Sb₂O_5-Pd-doped SnO₂ Pd coated layer, Al₂O₃-doped ZnO and PdCl₂-doped SnO₂. The portable electronic nose system consists of an l6bit Intel 80c196kc as CPU, an EPROM for storing system main program, an EEPROM for containing optimized connection weights of artificial neural network, an LCD for displaying gas concentrations. As an application the system has been used to identify 26 carbon monoxide/hydrocarbon (CO/HC) car exhausting gases in the concentration range of CO 0%/HC 0 ppm to CO 7.6%/HC 400 ppm and the identification has been successfully demonstrated.
공침법으로 제조된 $\textrm{SnO}_2-\textrm{In}_2\textrm{O}_3$ 계의 가스감응특성 및 감응기구
윤기현,임호연,권철한,윤동현,김승렬,홍형기,이규정,Yun, Gi-Hyeon,Im, Ho-Yeon,Gwon, Cheol-Han,Yun, Dong-Hyeon,Kim, Seung-Ryeol,Hong, Hyeong-Gi,Lee, Gyu-Jeong 한국재료학회 1998 한국재료학회지 Vol.8 No.9
Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism. 공침법을 이용하여 $\textrm{In}_{2}\textrm{O}_{3}$가 0-10 wt.% 첨가된 $\textrm{SnO}_{2}$ 계 미세 분말을 합성한 후, 스크린 인쇄법(screen printing)으로 후막형 가스센서를 제조하고 탄화수소($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) 가스에 대하여 가스 감응 특성을 조사하였다. $\textrm{In}_{2}\textrm{O}_{3}$는 $\textrm{SnO}_{2}$의 입자 성장을 억제시키기 위하여 첨가해 주었는데, $600^{\circ}C$에서 하소한 후에도 수 nm 크기의 미세한 입자를 얻을 수 있었다. 공침시 pH 값은 $\textrm{SnO}_{2}$ 의 입자 크기에 영향을 거의 미치지 않은 반면, $\textrm{In}_{2}\textrm{O}_{3}$ 첨가량은 입자 크기와 미세 구조에 큰 영향을 주었다. $\textrm{In}_{2}\textrm{O}_{3}$ 첨가량이 증가할수록 입자 크기는 감소하고 비표면적은 증가하였으며, 센세의 동작 온도를 약 $500^{\circ}C$로 하여 측정한 가스 감응 특성은 3wt.% 첨가했을 때 최대 감도를 나타내고 그 이상의 첨가량에서는 오히려 저하되었다. 3wt.%의 In2O3첨가시 $\textrm{SnO}_{2}$의 입자 크기와 비표면적은 각각 9.5nm, 38$\m^2$/g이었다. 임피던스 측정으로부터 얻은 단일 반원의 Nyquist curve와 선형의 전류-전압(1-V)특성 곡선으로부터, $\textrm{In}_{2}\textrm{O}_{3}$를 첨가하여 수nm로 입자 크기를 억제한 $\textrm{SnO}_{2}$ 계 가스센서는 미세 입자들끼리 형성한 치밀한 응집체와 이들 간의 계면(boundary)에 의해서 가스 감응 특성이 영향을 받음을 알 수 있었다.