Design of sensitive and selective gas sensors using microelectromechanical systems
- 주제(키워드) microelectromechanical systems , MEMS , gas sensors , nano technology , nano materials
- 발행기관 고려대학교 대학원
- 지도교수 주병권
- 발행년도 2013
- 학위수여년월 2013. 2
- 학위구분 박사
- 학과 일반대학원 전기전자전파공학과
- 세부전공 전자전기컴퓨터공학 전공
- 원문페이지 118 p
- 실제URI http://www.dcollection.net/handler/korea/000000038429
- 본문언어 영어
- 제출원본 000045745840
초록/요약
Over the past several years, great deals of research efforts were directed toward the development of miniaturized gas sensors, particularly for toxic gas vapor detection and for pollution monitoring. Though various techniques and materials are available for gas vapor detection, carbon nanotubes and metal oxides semiconductors are widely studied materials and their sensitivities for different gaseous species have been investigated. In this study, high performance gas sensors were designed and fabricated using MWCNT/SWCNT and metal oxide nanofibers as the sensing materials on micro platforms using MEMS technology. The roles of materials nano-structure and adding polymer and metal catalyst in the enhancement of the gas sensing characteristics have been investigated for chemical gas sensor applications. Measurements of the variation of vacuum level inside of field emission device when electron is emitted from MWCNT by electric field were performed. MWCNT gauge packaged with a vacuum device is used to measure the degree of a vacuum until the end of the vacuum device life. It was found that the electrical properties of MWCNT altered with the degree of a vacuum. I designed and fabricated MWCNT gauge which were printed and pasted by the screen printer. I report the fabrication of a novel gas sensor that utilizes the electrical resistance changes in electrically conductive PANI/Pd-NPs and SWCNTs composite materials, and its sensing property when NH3 and CO gases coexisted. In addition, I investigated the concentration dependence of electrical properties of PANI/SWCNT and SWCNT-Pd composite materials at room temperature using real time monitoring. The sensing properties and effect of PANI/SWCNT and SWCNT-Pd were demonstrated, and each sensor with good repeatability and fast response over a range of concentrations may be used as a simple and effective noxious gas sensor. Gas sensors were designed and fabricated using oxide nanofibers as the sensing materials on micro platforms using micromachining technology. Pure and Pt doped SnO2 nanofibers were prepared by electrospinning and their H2S gas sensing characteristics were subsequently investigated. The sensing temperatures of 300 and 500 oC could be attained at the heater powers of 36 and 94 mW, respectively, and the sensors showed high and fast responses to H2S. The responses of 0.08 wt% Pt doped SnO2 nanofibers to 4-20 ppm H2S, were 25.9 – 40.6 times higher than those of pure SnO2 nanofibers. The gas sensing characteristics were discussed in relation to the catalytic promotion effect of Pt, nano-scale morphology of electrospun nanofibers, and sensor platform using micro heater.
more목차
ABSTRACT i
TABLE OF CONTENTS iv
LIST OF FIGURES viii
LIST OF TABLES xiii
LIST OF IMPORTANT ABBREVIATIONS xiv
CHAPTER 1. Introduction 1
CHAPTER 2. Literature Survey 4
2. 1. Gas sensing mechanism of carbon nanotube sensors 4
2. 2. Gas sensing mechanism of metal oxide semiconductor sensors 7
2. 3. Enhancements of gas sensing characteristics 13
2. 3. 1. Morphological design for high performance gas sensors 13
2. 3. 2. Effect of catalyst loading 17
2. 4. Reference 21
CHAPTER 3. Design of a multi-walled carbon nanotube field emitter with micro vacuum gauge 25
3. 1. Introduction 25
3. 2. Experimental 26
3. 3. Results and Discussion 31
3. 4. Summary 38
3. 5. Reference 38
CHAPTER 4. Gas sensing performance of composite materials using conducting Polymer /Single-walled carbon nanotubes 40
4. 1. Introduction 40
4. 2. Experimental 43
4. 3. Results and Discussion 44
4. 4. Summary 53
4. 5. Reference 53
CHAPTER 5. Noxious gas detection using carbon nanotubes with Pd nanoparticles 56
5. 1. Introduction 56
5. 2. Experimental 57
5. 3. Results and Discussion 61
5. 4. Summary 67
5. 5. Reference 67
CHAPTER 6. Enhanced H2S sensing characteristics of Pt doped SnO2 nanofibers sensors with micro heater 71
6. 1. Introduction 71
6. 2. Experimental 73
6. 3. Results and Discussion 78
6. 4. Summary 91
6. 5. Reference 91
CHAPTER 7. Conclusions 94
ACKNOWLEDGEMENT 97
