Single-walled Carbon Nanotubes Catalytic Cracking Preparation And Variable Temperature Raman Spectroscopy Study

Since the discovery in 1993, SWCNTs have been the subject of focused studies in many fields because of their unique structural, physical and chemical properties and hence remarkable potential as a new material in a wide range of applications. With this concern, the synthesis and characterization of SWCNTs have been an area of intense research since then.The preparation of SWCNTs is a key part of research about SWCNTs, and the preparation of SWCNTs with good quality is precondition and foundation of characterizing structure, testing properties and further study in application. SWCNTs are produced by three main techniques: arc discharge, laser ablation and chemical vapor deposition(CVD). Nowadays, the CVD method appears to be a promising technique since it has a potential for a large-scale synthesis of high-quality SWCNTs at relatively low cast. The SWCNTs growth by CCVD is strongly affected by catalysts, growth time and synthesis temperature and so on. The formation mechanism is still not well established and the understanding of the catalytic growth of SWCNTs lags behind. Hence it is of great significance to study the growth mechanism of SWCNTs.With narrow bands, Raman spectroscopy has advantages for probing molecular structures, and has been proved to be a useful tool to analyze the structure of SWCNTs. However, the information it provided is limited by its low sensitivity. Change-temperature Raman Scattering has high sensitivity and resolution, which has been used as a powerful technique for providing high-quality spectra exhibiting fine structural details of molecules. Use change-temperature Raman Scattering for studying CNTs, high quality spectra have been observed and more structural details of CNTs have been obtained.The followings are the main results obtained in this paper:1,The SWCNTs were synthesized by the ACCVD (Alcohol Catalytic Chemical Vapor Deposition) method using the fluidized-bed as the reactor. The ethanol vapor was introduced into the fluidized-bed by the flow of Ar. Then the as-grown SWCNTs were characterized by Raman spectroscopy and SEM,TEM photos.2,A series of SWCNTs sample were synthesized with different flow rate of Ar at different reaction temperatures during the process of the synthesis. The results show that when the flow of the rate of argon was 150sccm, the quality of synthesized SWCNTs was fine. the flow of the rate of argon was more or less, the content of the amorphous carbon and Multi-walled Carbon Nanotubes(MWNTs) increased.3,SWCNTs synthesis temperature windows have been given by Raman spectra. The synthesis temperature window becomes narrow and the lowest synthesis temperature and the best synthesis temperature increase with the increase of the Mo content in the catalyzer.4,The Raman spectra of SWCNTs under change-temperature using resistance heat method. The results indicate that the temperature dependence of RBM at low temperature is greatly different from that at high temperature. The relative Raman intensities of different conducting SWCNTs change when the temperature changes.