(235e) Experimental Research on Flame Synthesis of Carbon Nanotubes and Its Growth Mechanism Analysis

Carbon nanotubes are usually considered as graphite sheets rolled-up into cylinders with diameters as small as several nanometers. Extensive research about the properties of carbon nanotubes such as the optical properties, electrical transport, vibration properties, mechanical and thermal properties have made great achievements. At present, carbon nanotubes are mainly produced by arc-discharge, laser vaporization, CVD, and pyrolytic method. These methods are low in energy utilized rate. Flame synthesis of carbon nanotubes is a kind of novel technique, it provides basic reaction conditions such as enough energy, hydrocarbon and high temperature for synthesis of CNTs. It is the potential method to product carbon nanotubes in large scale. In this paper, an experimental system to synthesize carbon nanotubes based on diffusion flames is developed. Different bulk metal catalysts are used for CNTs synthesis. The experimental results show that the production of CNTs is influenced by flame type, catalyst material, reactant gas composition, synthesis temperature, sampling point, etc. The effect of catalyst and gas mixture on CNT synthesis is judged on the basis of the morphology of the CNTs observed by SEM and their graphitic structure observed by TEM. The optimum experimental conditions for CNTs synthesis, including temperature, metal catalyst and reactant gas, is obtained from experiments. At last, the growth mechanism of CNTs including Yarmulke mechanism, three steps mechanism, base growth mode, CSDP mechanism and segregation growth mechanism are analyzed. Key words: Carbon Nanotubes (CNTs); Flame Synthesis; Growth mechanism