Gas Sensors Based On Nano-zeolite And Carbon Black Polymer Sensitive Film

Two parts of research have been done in this thesis "the study of gas sensor based on nano-zeolite and carbon black polymer films"In the first part, the gas sensor based on nano-zeolite film has been studied to detect the nerve simulate gases. This sensor presents high sensitivity, quick response and the miniaturigation. This research work will provide a novel way to quickly detect the nerve agent gas in order to fight against terrorism and chemistry war.The study of the sensor based on the conventional zeolite film to detect the inorganic gas has been reported previously. The minimum detectable concentration is 40ppm, the sensitivity is 0.5Hz/ppm, and the response time is 4000 seconds. However there was no report on the detection of the nerve agent gas using nano-zeolite film.In this thesis, a novel nano-zeolite film with the property of quick response to nerve agent Sarin simulate DMMP gas, dimethylmethylphosphonate (DMMP) , is studied. The chemical synthesis of the nano-zeolite and reproducibility, selectivity of the gas sensor based on nano-ZSM-5, nano-Ag+ZSM-5 and beta zeolite with different size and microstructure are studied. The relationship between the response to DMMP and the hole size as well as the microstruction of zeolite film is obtaind. The results show that the nano-ZSM-5 zeolite has good sensitivity to DMMP.In order to examine the properties of zeolite as the sensing material, a prototype of gas sensor based on the nano-ZSM-5 film with the quartz crystal microbalance (QCM) is fabricated. To improve the precision of the measurement, a special high frequency quartz crystals and the different frequency measurement system have been used to eliminate the system error. The frequency shift was 60Hz for 1ppm DMMP gas.The desorption of the DMMP is one of the key technologies for the gas sensor based on the nano zeolite films. It is difficult for a full desorption of the DMMP using traditional desorption method such as the high temperature treatment in the nitrogen. In this thesis, a novel desorption method for strong polar molecule DMMP using high frequency alternate electric fields is proposed. The result shows that the desorption time decreases from 100s to 20s by using the method with the high frequency alternate electric field against traditional desorption methods.In a word, the novel nano zelite sensing material for detecting the nerve agent Sarin simulates DMMP is first reported in this thesis. The prototype of the gas sensor based on the nano-ZSM-5 film for detecting DMMP is obtained. The sensor has high sensitivity of 60Hz/ppm. A novel desorption method with high frequency alternate electric field is proposed to solve the key problem of desorption for nano zeolite films. The results show that using nano zeolte film as a sensing material for Sarin simulates gas is a promising technology.The second wok in this thesis is the study on a novel polymer carbon black material, which is sensitive to the organic gas. The structures of the interdigitated microelectrode array with different patterns and different width to the length ratio are designed. A prototype of chemoresistor sensor based on carbon black polymer films is obtained. The organic gas and their mixed gas at low concentration are detected.The advantages of the macromolecule polymer material are lower cost, simple fabrication, the compatibility with the IC process, lower synthesis temperature and so on. So a lot of researches in the world have been devoted to the development of the macromolecule polymer as a sensing material. The adsorption of gas onto the polymer with carbon black material can produce a change in its electrical resistivity and this resistivity change is easy to measure. The study on the chemoresistor sensor based on the polymer carbon black has been reported. However the stability and selectivity of the polymer carbon black have to be studied farther.A novel micro sensor array based on carbon black polymers has been studied in the thesis. The dependence of the sensing properties on the thickness of the film and the microelectrode pattern is studied. According to the size of the sensor chip and the characteristic of the noise, interdigitated microelectrodes arrays with large width to length...