Study On Flow Sensing Characteristics Of Carbon Nanotubes Thin Film

Since carbon nanotubes (CNTs) discovered, as a new quasi-one-dimension nanomaterial, CNTs have unique geometry structure and fantastic physical, chemical characteristics leading to many potential applications. Especially their electronic characteristics make CNTs useful in researching and developing nano-device. CNTs always have attracted worldwide attentions for several years, therefore, they become a leading edge problem in international nanomaterial research field. CNTs as sensor material, both here and abroad started correlation experiment, theoretical investigation and provided possibilites of practical application. In this paper, chemical modification for CNTs, preparation of CNTs thin films, CNTs thin films fundamental characteristics and flow sensing characteristics were investigated experimentally and theoretically.The functional modification of carbon nanotubes has been obtained by mixed acid and thionyl chloride treatment, both treated CNTs and untreated ones were indicating analyzed by Infrared Ray and Transmission Electron Microscope. CNTs thin films were prepared by solution aggradation, and Atomic Force Microscope was used to indicate the CNTs thin film.Electric conduction mechanism was discussed by study on the relationship between resistivity and temperature.Finally, the resistivity formula of CNTs thin film was validated by the experiments.Sensing characteristics of CNTs thin film included sensing characteristics of MWNTs thin film in flowing solutions and sensing characteristics of SWNTs thin film in rotational solutions. It was experimentally found that the sensing characteristics of MWNTs thin film in flowing solutions had great affinities with the kinds,the concentration and the velocity of the solutions. The induced voltage produced by thin film would increase as the increase of concentration and velocity. In the range of the solutions chose in our experiments, the sensing characteristics of thin film in HCl solutions were the best ones. However, the sensing characteristics of thin film in KCl solutions were the worst ones. The sensing characteristics of thin film would be greatly increased by modified with mixed acids. The sensing characteristics of modified thin films were ten times of that of unmodified thin films.Flow Sensing mechanism of CNTs thin film was discussed in this paper, double electricity layers model was used to discuss the results obtained from our experiments. Then the model was modified based on our experiments. Through synthesis study of experiments and theories, the sensing characteristics also had affinities with the charge-to-mass ratio of the ions in the solutions. The sensing characteristics of SWNTs thin film in rotational solutions also had great affinities with the kinds,the concentration and the rotational speed of the solutions. Two-dimension solid monolayer model was established to discuss the results obtained in rotational experiments.