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研究生：	黃浩軒 Huang, Hao-Hsuan
論文名稱：	薄帶製程及擴散障礙層最佳化對空燃比含氧感知器性能之研究 Optimization of Diffusion Barrier and Tape Casting for Air-Fuel Ratio Oxygen Sensor
指導教授：	方冠榮 Fung, Kuan-Zong
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學及工程學系 Department of Materials Science and Engineering
論文出版年：	2019
畢業學年度：	107
語文別：	英文
論文頁數：	71
中文關鍵詞：	寬域含氧感知器、薄帶製程、擴散障礙層
外文關鍵詞：	air-fuel ratio sensor, tape-casting, diffusion barrier
相關次數：	點閱：42 下載：0
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由於環保意識的提高，環境問題引起了每個人的更多關注。現在，監管變得更加嚴格。為了趕上這種嚴格的排放法規，幾乎所有的汽油動力車都配備了觸媒轉化器來處理排氣污染物NOx，CO和HC。雖然觸媒轉化器可以消除部分有害氣體。為了改善空污現況，應控制燃燒在最適當的空燃比條件下，進行完全燃燒，以有效減少污染物的產生。在引擎燃燒過程中，空燃比是控制燃料消耗和污染物生成的關鍵。在排污系統中，在排氣管內通常會放置兩支含氧感知器，靠近引擎的含氧感知器於監測燃燒過程中空燃比的偏差並且傳送訊號給引擎控制元件(Engine Control Unit, ECU)；放置於觸媒轉換器後方的含氧感知器則是提供訊號與前方含氧感知器訊號比較後，監控觸媒轉換器的功能是否正常。
傳統的的電壓式含氧感知器，在無法真正有效的鑑別排出廢氣中精準的含氧量，對節省油耗以及降低污染仍嫌不足。因此本研究致力於最先進的電流式寬域含氧感知器(Wideband Oxygen Sensor)。寬域含氧感知器可精準偵測濃油或稀油燃燒下廢氣含氧量，進而有效地改善燃燒效率及空汙防制。然而寬域含氧感知器的製備要求高，包含具氧離子導性之氧化鋯功能性材料合成及多層結構之設計與厚膜技術製程。除了標準的刮刀成型製備厚膜外，擴散障礙層(Diffusion Barrier)為影響感知電流之關鍵因素，其功能為控制氣體的擴散至腔體內的流速，進而由偵測到的極限電流判斷廢氣含氧量。本研究中，藉擴散障礙層不同孔隙率的設計及產生收縮率，觀察其對含氧感知器感測性能之影響。例如當孔隙率為23%時，感測器呈現最佳的感測性能，且其收縮率和生胚的收縮率達成良好匹配。另一個重要部分是加熱器的整合。為了使感測器在最短時間發揮其效能，以有效的降低啟動汙染時間，必須設計內建加熱器，換言之，加熱器須與感測器整合為一體。本研究中，也探討兩種不同加熱器設計，並分析其加熱時之升溫速率與溫度維持之穩定性。結果發現，採用並聯式加熱器具有較高穩定性與加熱之均勻性。例如，內建20W的加熱器，可於3秒內加熱至300°C，可以達到560°C的平衡溫度。，可望於汽車引擎發動後，短時間即可有效監控廢氣的排放。經內建20W的加熱器整合後的寬域含氧感知器，模擬於汽機車排氣管之高溫環境，將感測器至於不鏽鋼管內，升溫至實際排氣管溫度，進行氣體感測性能測試。經由通入不同濃度之O2(0.6vol%-25vol%，由濃油至稀油)之模擬氣體進行感測性能測試。在維持600°C工作溫度下，其感測器可偵測濃度範圍為，在O2 濃度0.6vol% 到25vol% ，意即應證本研究所開發之感測器可應用於寬域感測。經過循環測試，訊號經過500圈循環後，訊號誤差在1%的範圍內，顯示此感測器具有長期使用之穩定性。

Due to the increased awareness of environmental protection, environmental issues have attracted more attention from everyone. Now, regulation has become stricter. To catch up with this strict emission regulation, almost all gasoline-powered vehicles are equipped with catalytic converters to treat exhaust pollutants NOx, CO and HC. In order to improve the current situation of air pollution, the combustion should be controlled under the most appropriate air-fuel ratio conditions for complete combustion to effectively reduce the generation of pollutants. Air-fuel ratio is the key to controlling fuel consumption and pollutant generation during engine combustion. In the combustion system, two oxygen sensors are usually placed in the exhaust pipe, and the oxygen sensor near the engine monitors the deviation combustion process and transmits signals to the Engine Control Unit (ECU); The oxygen sensor placed behind the catalytic converter is to provide a function of monitoring the catalytic converter after comparison with the front oxygen sensor signal.
The traditional potentiometric oxygen sensor is not effective in identifying the accurate oxygen content in the exhaust gas, which is still insufficient for saving fuel consumption and reducing pollution. Therefore, this research is dedicated to the most advanced current Wideband Oxygen Sensor. The wideband oxygen sensor can accurately detect the oxygen content of the exhaust gas under fuel rich or fuel lean condition, and improves combustion efficiency and air pollution control. However, the wideband oxygen sensor has high requirements for preparation, synthesis of zirconia materials with oxygen ion conductivity, and design of multilayer structure and thick film technology. In addition to standard tape-casting process, diffusion barrier is the key factor affecting the sensing current. Its function is to control the flow rate of gas diffusion into the cavity, and then detect the limiting current to determine the oxygen content in the exhaust gas. In this study, we discuss the effect of different porosity and shrinkage at diffusion barrier layer to sensing performance of the oxygen sensor. For example, when the porosity is 23%, the sensor exhibits the best sensing performance, and its shrinkage is match with YSZ green tape. Another important part is the integration of the heater. In order to reach the operation temperature of oxygen sensor more quickly, it is necessary to design a built-in heater integrated with the sensor. In this study, two different pattern heaters are discussed with their heating rate and stable temperature. As a result, it is found that the parallel type heater has high stability and uniformity heating region. For example, a 20W heater can be heated to 300 ° C in 3 seconds, which can reach a stable temperature of 560°C. It is expected that after the engine starting, the exhaust gas emissions can be effectively monitored in a short time. The wideband oxygen sensor integrated with the built-in 20W heater simulates the high temperature environment of the exhaust pipe. The sensor is placed in the stainless steel tube and heated to the actual exhaust pipe temperature for gas sensing performance test. Sensing performance tests were performed by simulated gases with different concentrations of O2 (0.6 vol% - 25 vol%, from fuel rich to fuel lean). This sensor can detect the O2 concentration range from 0.6 vol% to 25 vol% while maintaining the operating temperature of 600 °C, which means that the sensor developed by this study can be applied to wide-range. In the cycle test, after 500 cycles sensing, the signal error is within 1%, indicating that the sensor has long-term stability.

Chapter1 Introduction	1
Chapter 2  Literature Review	3
2-1 Sensing Principle of Oxygen Sensors	3
2-1-1 Potentiometric Sensors (λ-type sensors)	4
2-1-2 Thimble type and planar type oxygen sensor	6
2-1-3 Amperometric Sensors (Limiting-Current type Sensors)	9
2-1-4 Disadvantage of single-cell limiting-current sensor	12
2-1-5 Characteristic of dual-cell limiting-current oxygen sensor	13
2-1-6 Comparison Diffusion Barrier of Hole and Porous Layer Type	16
2-2 Solid electrolyte in oxygen sensors	18
2-2-1 Characteristic of Yttria Stabilized Zirconia (YSZ)	18
2-3 Tape casting process	21
2-3-1 Solvent	21
2-3-2 Binder	21
2-3-3 Plasticizer	22
2-4 Motivation	23
2-5 Objective	24
Chapter 3   Experiment	25
3-1   Experimental procedure	25
3-2 Chemical in the study	26
3-3 Powder preparation	27
3-3-1 Synthesis of YSZ powder by Solid-State Reaction	27
3-3-2 Synthesis of TiO2 dopped-precursor of Al2O3 powder by Solid-State Reaction.	27
3-4 Manufacture of Tape Casting Slurry and Screen-Printing Slurry	28
3-4-1 Manufacture of Tape Casting Slurry	28
3-4-2 Manufacture of screen printing slurry	29
3-5 Pattern Design for Screen Printing	30
3-5-1 Heater pattern design	30
3-6 Test and analysis	31
3-6-1 X-ray diffraction (XRD)	31
3-6-2 Scanning electron microscope (SEM)	31
3-6-3 Infrared thermography (IRT)	31
Chapter 4  Result and Discussion	32
4-1 Ceramic Lamination and Tape-Casting Technology	32
4-1-1 Slurry with Different Solid Loading	32
4-1-2 Pressure and Temperature Effect on Laminated Oxygen Sensor	36
4-2 Heating performance of a heater	39
4-2-1 Shrinkage mismatch between insulation layer and YSZ green tape	41
4-2-2 Heater Performance	43
4-2-3 Heating Cycle Testing	49
4-3 Fugitive layer preparation	52
4-4 Sensing test of oxygen sensor with diffusion barrier	54
4-4-1 Principle of diffusion barrier	54
4-4-2 Diffusion barrier prepared by Al2O3 and starch pore former	55
4-5 Sensing Performance of Air-Fuel Ratio Sensor	57
4-5-1 Sensing performance of dual-cell limiting-current oxygen sensor	57
4-5-2 Temperature dependence of dual-cell oxygen sensor	63
4-5-3 Sensing cycle test	66
Chapter 5 Conclusions	68
Reference	69


                                    

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校內：2024-07-18公開
校外：2024-07-18公開

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