In Situ Synthesis Of Carbon Nanotubes By Catalytic Pyrolysis At Low Temperature

In 1991, carbon nanotube (CNT) was first reported in Nature by Iijima.From then on CNT has become the focus of intense interest of scientists inthe field of physics, chemistry and materials all over the world. During thelast decade, some industrial applications have been anticipated forsingle-walled and multi-walled CNT. Among many factors, their future usewill strongly depend on the development of new technologies forlarge-scale production at low temperature. In this work, a novel and simple method is explored to prepare relativegood quality CNT with a significant production yield at 500℃. Due to this,the as-prepared CNT probably can be put into a wider range ofapplications. For the production of CNT, ferrocene, nickel( Ⅱ )acetate.4H2O, cobalt(Ⅱ) acetate were used as the catalyst precursorsrespectively, and n-hexane as the carbon source. After investigation of themorphology and micro-structure of the products, a series of researchconclusions are obtained. (1) Ferrocene as the catalyst precursor Carbon nanofibers with the diameters of 30-50nm co-exist withnano-particles in the product. The hollow cavity of the nanofibers is notclear. There are particles in large size sticking between the fibers.(2) Nickel(Ⅱ) acetate.4H2O as the catalyst precursorThe products take on a kind of helix microstructure. The ratio ofnanofibers in the product increases distinctly compared with the productsabove. The microwave permittivity of the products suggests a potentialmethod to synthesize some composite materials with some wantedelectromagnetism parameter. (3) Cobalt(Ⅱ) acetate as the catalyst precursor A typical TEM micrography of the product shows a large area of pure CNT, with few catalyst particles wrapped in upper area of the IIItubes, and there is almost no trace of amorphous carbon and multishellcarbon nanocapsules. The hollow cavity with the diameter ranging from 40to 80 nm can be clearly seen from the higher magnification image, whenadding more n-hexane to raw reagent. The 002 lattice fringe imagesobserved by HRTEM show the well-developed carbon layers, however,some defects can also be seen, suggesting the existence of disorderedcarbon. The average yield was more than 16g under the condition of1.0g/120ml. The ratio of insoluble solid is above 80% after boiling inhydrochloric acid (37%) for 2h. The synthesis method is simple and can easily ensure adequatestability and reproducibility. Therefore the method possibly is suited toapply to industrialized synthesizing process of CNT due to theseadvantages.