Single-walled Carbon Nanotubes, Preparation And Characterization Of Chemical Vapor Deposition

The synthesis process of single-wall carbon nanotubes (SWNTs) by catalytically chemical vapor deposition (CCVD) was investigated and the product was characterized with transmission electron microscopy (TEM), electron diffraction (ED), electron dispersive spectra (EDS) and Raman scattering spectra etc. Pyrolysis of methane over solid catalysts prepared with impregnation, ion-adsorption precipitation, and sol-gel technique can all lead to the growth of SWNTs. While sol-gel technique was optimized, the yield of SWNTs was improved and the radial breathing mode (RBM) of them appeared in Raman spectra. Furthermore, we also achieved bulk production of multi-wall carbon nanaotube bundles.The experimental results indicated that the preparation of catalysts played a key role in the yield and quality of SWNTs. Plentiful and pure SWNTs were grown over the catalyst prepared by the sudden blast of slurry containing citric acid. This kind of catalyst was very fine, with strong interaction between the support and the active component particle, and high dispersion of such particles on the surface of the support. Yield of carbon nanotubes can also be improved greatly by the doping of molybdenum to catalyst. While still not evidenced in our experiment, liquid-phase doping of ammonium molybdate solution has been broadly agreed to be able to significantly increase the yield of SWNTs. We have developed another doping method, solid-phase doping of metal molybdenum at elevated temperature, and discovered that sol-gel prepared catalyst with such doping can be used to grow multi-wall carbon nanotube bundles in a very large scale. Our results have also showed that different optimal growth conditions should be applied to different catalysts, due to the different interaction between the supports and the active component particles.