Preparation Of Single-walled Carbon Nanotubes, Purification And Raman Spectroscopy

With remarkable structural,physical and chemical properties, single-walled carbon nanotubes (SWCNTs) can be explored to be used in novel applications and become a hotspot of studies on nano material. Since the discovery of in 1993, the synthesis, purification and characterization of SWCNTs have been an area of intense research.There are many techniques for nanotubes synthesis. SWCNTs are generally produced by three main techniques: arc discharge, laser ablation and chemical vapour deposition(CVD). Nowadays, the CVD method appears to be a promising technique since it has the potential for a large-scale synthesis of high-quality SWCNTs at relatively low cost.Most approaches in general produce powders containing not only CNTs but also other carbonaceous particles such as amorphous carbon, fullerenes, nanocrystalline graphites, and metals that were introduced as a catalyst during the synthesis. This sometimes hinders an accurate analysis of the CNTs characteristics and limit the best performance of CNTs application to new functional devices. Several attempts have been tried to purify the CNTs powders, such as size exclusion chromatography, filtration methods, selective oxidation processes, or a combination of these methods. Among these methods, thermal purification in air exhibits remarkable advantages, the simple process and efficiency in purifying guarantee an easy possibility to scale purification at low cost.Raman spectroscopy can be used as one of powerful techniques for the study of SWCNTs. Informations such as the structural and physical properties of the SWCNTs can be abtained from Raman spectra.The followings are the main results abtained in this paper1 .. The SWCNTs were synthesized from natureal gas. By studying the Transmission Electronic Microscopy (TEM) and Raman spectra of products obtained from different catalysts at the same temperature, we found that Mo₁Fe₁₀ was the optimal catalyst for synthesizing SWCNTs from natural gas. And the window of synthesis temperature, the yield of carbon and the quality of were studied.2-. Because of the special effect of water on carbon nanotubes, we studied the effects of water .which was introduced into the reactor from a bubbler for 0,10,20 and 30min, on theproducts by TEM and Raman spectra. And the reaction of water and carbon was discussed..3 A technique of purifying SWCNTs had been developed by means of oxidizing carbonaceous particles with air using fluidized-bed. Air was introduced into the fluidized-bed by pump with controllable flux. The fluidized-bed was applied as the heating apparatus instead of rotated quartz tubes. The air and the powders could be mixed with each other more sufficiently. Characteristics of the raw and purified powder were presented using Raman spectroscopy and Transmission Electronic Microscopy (TEM), revealing that the purified powder is free from carbonaceous particles.4 High quality Raman spectra of SWCNTs had been obtained in the mixed alcohol and dropped on the surface of the slices of iron, aluminum, silicon, silver ablated by laser; the film of silver and gold. The intensity of raidal breathing modes (RBM) increased obviously. The results showed that the roughness and nano particles affected the intensity of RBM.