Under the dome, we share the same fate as breathing. The importance of air to human beings is self-evident. Entering the 20th century, with the rapid development of world industry and the sharp increase in population, the number of motor vehi cles keeps increasing. The shortage of resources and the environmental pollution caused by exhaust emissions are becoming increasingly prominent. It has become a severe challenge for the sustainable development of the automobile industry. Nitrogen oxides in exhaust gas are to be blamed because they cause problems such as acid rain, photochemical smog, and ozone hole. They seriously damage the ecological environ ment and endanger human health. Therefore, many countries in the world have put forward strict limit standards for nitrogen oxides emitted from motor vehicle exhaust. It is necessary to accurately measure and control the nitrogen oxides (mainly NO2) produced by automobiles.
There are many kinds of gas detection methods. Although instrument analysis methods such as gas chromatography, mass spectrum, and spectrum, have high accu racy, they are complicated to be operated, high in cost, and difficult to be integrated. So, they cannot meet the requirements of in-situ detection of automobile exhaust. With the development of sensor technology and material science, researchers have found that Yttrium Stabilized Zirconia (YSZ), a solid electrolyte material has the advantages of high temperature resistance, high humidity resistance, stable chem ical and mechanical properties, etc. Based on this material, gas sensors can not only meet the limit of automobiles confined space on the instrument use, but also can be better suitable for harsh working environments. They are showing great application potential in the field of high-temperature gas detection.
The theme of this book is the technical research related to gas sensors. The key technologies of mixed potential gas sensors based on YSZ are mainly divided into three aspects: sensitive material, electrochemical reaction process, and device manu facturing process. On the basis of a systematic analysis of the existing research work, the author of this book has extracted the key scientific problems existing in sensors, and has given corresponding solutions and verifications. As an important medium for the identification and conversion of gas information, sensitive material is the prerequisite for gas-sensitive characteristics of NO2 sensors. Firstly, starting
from the research of sensitive material, we have carried out research and innovative design on the components and nanostructures of NO2-sensitive materials, and devel oped a low-cost, easy-to-synthesize, high-sensitivity, and selectivity gas-sensitive nanocomposite material. It has greatly improved the basic performance of NO2 sensors. Secondly, the electrochemical reaction process is an important part of the solid electrolyte gas sensor. Based on the mechanism study of the three-phase reac tion interface constituted by electrolyte, sensitive material, and NO2gas, we innova tively propose a highly efficient, environment-friendly, and controllable micro-nano structure which can build a large specific surface area, and a micro-nano processing method which can increase the number of active sites of electrochemical reaction. It can be applied to optimize the performance of any kind of solid electrolyte sensor. Finally, we focus on the device manufacturing problems which are less discussed in other research work. Through the combination of traditional ceramic material technology and modern MEMS technology, the YSZ mixed potential gas sensor realizes high consistency and batch processing for the first time. It also has low power consumption and is miniaturized. The device has good fiexible and mechan ical characteristics and can be applied to gas in-situ detection in high-temperature pipelines. This work has significantly reduced the dependence of current chemical gas sensors on human labor, and plays a very good role in promoting the sensor manufacturing industry.
In conclusion, this book introduces an interdisciplinary research result. It combines research achievements in fields such as instrumental science, material science, electrochemistry, and micro-nano electronics. Meanwhile, both theoretical and experimental works have been taken into consideration, and comprehensive inno vative research and detailed demonstration of key technologies of gas sensors have been completed. In this challenging subject, the author of this book has made an outstanding contribution. As a result, the performance and reliability of gas sensors have moved ahead. A new commercial manufacturing scheme for the sensor industry has been explored, taking into account both innovation and practicability. The main purpose of this book is to make the new gas sensor practical as soon as possible. It is also the starting point and direction for future researchers.
Prof. Tianhong Cui
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