Manipulation Of Carbon Nanotubes And It’s Mechanism Exploring

Research on one-dimensional (1D) nanostructure has been the focus of nanotechnology due to their importance in the fundamental research and potential applications. Among these 1D nanomaterials carbon nanotube is a hot topic due to their excellent physical properties and stable chemical property. They are considered as very promising materials for various applications, such as dioes and transistors. However, bulk samples of randomly oriented carbon nanotubes have exhibited substantially lower electrical and thermal conductivities than expected for individual carbon nanotubes. The most desirable approach for fully harnessing the properties of carbon nanotubes at the macroscale is one to provide a direct route for producing aligned carbon nanotubes. Aligned carbon nanotubes film is still a challenge for what might be electronics of the future.Therefore, in this dissertation, aligned carbon nanotubes were fabricated by modified arranging and transferring technique and the mechanism of the method was also studied. The major research results can indicate as follows:A simple, effective and non-destructive purification for single-walled carbon nanotubes synthesized by arc-discharge has been demonstrated in this paper after several trials. The appropriated conditions for these treatments were found to depend on the nature of the starting material. Accordingly, the reaction condition for each step needed to be carefully examined.To cutting and introduce carboxylic groups, these purified multi wall carbon nanotubes were further oxidized with H2SO4 and HNO3 for different hours at 60℃. The products were reacted with thionyl chloride to introduce acyl chloride groups into the carbon nanotubes, and then reacted with octadecylamine (ODA). The products prepared possess substantial solubility in chloroform, CS2, and other various aromatic solvents. The solution was visually non-scattering and no precipitation occurred for months. As the same time, the solubilized carbon nanotubes’solubility in a variety of organic solvents as well as the percentage content of tubes in the solubilized samples was determined. The results show the room temperature solubility of carbon nanotubes as a function of the solvent polarizability parameter.A reliable procedure to prepare aqueous dispersions consisting of long, individual single wall carbon nanotubes was explored. The key feature of the method is a sequence of different types of mild treatments, which minimizes tube shortening and allows maximal preservation of its structure and electronic properties, at the same time, the treated single wall carbon nanotubes increased in purity and specific surface area. The degree of dispersion and length of the tubes were monitored by AFM and SEM.Measurement of surface-area isotherms and thin films deposition were performed using KSV-5000 Instrument. A carbon nanotube solution was carefully spread on pure water surface in the Langmuir trough. After the solvent evaporated, these CNTs were then compressed by moving barrier at a constant speed. The substrate used for the deposition films should be firstly treated to produce hydrophobic or hydrophilic surface. Arranging and transferring technology has been applied to build homogeneous thin films of chemical solubilized carbon nanotubes , which possess good surface spreading properties at the air/water interface. Deposition can be performed in a layer-by-layer fashion to 100 or more layers either by horizontal lifting or vertically dipping, allowing to readily control the film thickness. Highly aligned carbon nanotubes were fabricated by the vertically dipping method. The aligned carbon nanotubes film quality can be controlled by adjusting the parameters such as surface pressure, temperature, compress speed, dipping speed, the contact angle, the length of the carbon nanotubes and solvents. Scanning electric microscope (SEM), atomic force microscope (AFM) and polarized Raman absorption spectroscopy observation demonstrate that the carbon nanotubes are oriented in the direction of the trough barrier (horizontal lifting) or in the dipping direction (vertical dipping). These are attributed to compression-induced or flow-induced orientation, respectively, the later found to be much stronger than the former. The realization of homogeneous thin film of carbon nanotubes with a controllable thickness and tube orientation should be an important basis for the future development of their scientific understanding and technological application.Lastly, the mechanism of the manipulation of carbon nanotubes was established based on the experimental, accompanied by a thermodynamic and kinetic analysis. The purpose of focusing the analysis of the arranging and transferring technique is designed to serve as a blueprint for future analysis of the arranging and transferring technique. The main objective of the study is to point out the close relationship between the contact line dynamics and arranging and transferring deposition. Moving contact line and contact angle play a major role in the ultra thin film deposition. The flow patterns depend on dynamic contact angle and the ration of viscosities of the gas and liquid phases. The depositions are only possible when the flow patterns near the contact line results on the movement of the interface toward the contact line. The interface moves toward the contact line (the substrate) at a speed that determines transfer ration. The deposited films are highly ordered and show a number of interesting properties.