Study On Strong Selective Gas Absorption Film Of Surface Acoustic Wave Gas Sensor

The coal industry acts as the absolute dominant role in China's energy industry, and the coal mine safety especially the gas safety in mine is the most important thing. In recent years,much money and effort have been taken for the prevention of coal mine gas accidents. It is very important to invent novel gas sensor for reducing the event of gas explosion and gas outburst. Surface Acoustic Wave?SAW? gas sensor owns high sensitivity, small size, and it is easy to be wireless and integrated, and also it represents the development direction of coal mine gas sensors. Based on gas safety of coal mines, the adsorption mechanism of SAW gas sensor and development trend are analyzed, and the sensitive film of organic, inorganic and organic-inorganic composition were prepared by different methods. The strong selective gas adsorption film of SAW gas sensor is studied, which lays a solid foundation for this kind of sensor. This research contains the following key aspects:First, based on the first principles density functional theory?DFT? and the plane wave pseudo-potential method, the adsorption model of CH₄ on the SnO₂?110? surface is constructed. A variety of adsorption configurations and optimal adsorption sites are obtained by calculating the adsorption energies of different oxygen sites of CH₄. The surface and local electronic density of state are analyzed. The results show that the maximum adsorption energy of CH₄ on oxygen TOP position is-8.314 e V, which proves that SnO₂?110? thin films owns potentially strong selectivity for gas.Second, SnO₂ sol is prepared with sol-gel method and modified by SbCl₃ which is set as to improve the selective ability of films for gas. And it is deposited on a silicon substrate by using spin-coating method. Then the morphology and structure are characterized by XRD.The results show that the structure of SnO₂ film is tetragonal phase rutile structure with annealing treatment, and the diffraction peaks correspond to?110?,?101? crystal phase. The doping of Sb does not lead to the formation of new phase.Finally, the polyaniline?PANI? is synthesized and modified in an acidic environment withchemical oxidative polymerization by SnO₂ which is also set as to obtain highly selective performance for gas. Then the material is dissolved in N-methyl group and is prepared for film with Langmuir-Blodgett?LB? method. The composition, microstructure and morphology are characterized by means of AFM and XRD testing methods. The powder and thin film of PANI and PANI-SnO₂ are fabricated, and the results show that, the powder quality is very good, and the LB films need improve better, moreover this quality of film is proportional to the amount of membrane and the compression speed of the barrier of LB machine.The theoretical modeling method is applied to construct and prove that SnO₂ film owns highly selective performance for gas. The corresponding different SnO₂ film, Sb doped SnO₂ film, PANI film, and PANI-SnO₂ composite film are successfully fabricated, and related characterizations are made, and it need further research on the experimental investigation on the gas selection performance of those films, and it will be the key foundation for the highly accurate SAW gas sensors.