Abstract for presentation at Chemeca 2007

Carbon nanotubes (CNTs) are a form of crystalline carbon with unique properties. Currently, research into nanotubes and their applications is hampered by the lack of a suitable technique for manufacturing them in large quantities. Catalytic chemical vapour deposition using a fluidised bed reactor has been suggested as a potential large-scale synthesis technique. In this work we report on the results of a parametric study into the effects of i) synthesis temperature, ii) gas velocity, iii) catalyst type, iv) catalyst loading, and v) deposition time, on the nanotube synthesis in a fluidised bed reactor. The as-synthesized products were analysed using thermogravimetric analysis (TGA) and transmission electron microscopy (TEM).

The results from this preliminary study show that the carbon yield generally increased with increasing synthesis temperature. Higher temperatures produced CNTs with a better defined wall structures and less amorphous carbon. At 700ºC, coiled carbon nanostructures were observed. However, the temperature did not appreciably influence the diameter or length of the CNTs. Nor was a clear relationship between catalyst type (iron, iron-cobalt) and carbon yield observed. Interestingly, increasing the catalyst metal loading did not correlate with an increase in carbon deposition. A maximum total carbon and CNT yield, based on catalyst loading, of 204% and 87.6% respectively was observed, and the maximum CNT selectivity was 75%. Further work incorporating this study into an optimized statistical methodology is currently underway.