in Wiley InterScience (www.interscience.wiley.com).The synthesis of carbon nanotubes (CNTs) on a cobalt-iron (Co-Fe) catalyst supported on a calcium carbonate (CaCO 3 ) substrate, contained within a fluidized bed was investigated for the first time. CaCO 3 supported catalysts, prepared using traditional wet impregnation techniques result in a soft and sticky powder requiring special arrangements to ensure satisfactory fluidization. A modified method developed using citric acid complex resulted in CaCO 3 supported catalysts that can be classically fluidized without special arrangements. The issue of Fe 31 (aq) hydrolysis above its critical pH of ;3.5 was also addressed. A carbon yield consistently greater than 10 times the weight of the catalyst metal loading was obtained. Thermogravimetric analysis coupled with mass spectrometry showed a single peak centered on 5758C, with no peaks below 4008C, indicating that an insignificant quantity of amorphous carbon was present. Transmission electron microscopy verified that the products contained a large proportion of CNTs.

The interaction effects between temperature, catalyst properties, fluidization conditions, and deposition time during carbon nanotube (CNT) synthesis by chemical vapor deposition in a fluidized bed were investigated. While numerous investigations have attempted to correlate process parameters with CNT characteristics, selectivity and yield, the interaction between process parameters is often ignored. Parametric interactions in this process have been investigated using a factorial design methodology. Besides the main effects of synthesis temperature, deposition time, and catalyst type, the interaction parameters temperature−time and temperature−catalyst were found to significantly influence the resultant carbon and CNT yields. These results lay the foundation for a detailed parametric analysis toward the optimization of CNT synthesis in fluidized beds, which takes into account these interaction effects.

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The absence of large-scale carbon nanotube synthesis technology (which we define as being of the order of 10 000 tonnes per plant per year) is limiting research and development activities across the sector. We contend that fluidized bed chemical vapour deposition (FBCVD) is the most promising technology for large-scale, low-cost, carbon nanotube synthesis. In this work, multi-walled carbon nanotubes were synthesized on alumina-supported iron, cobalt, or nickel catalysts by catalytic chemical vapour deposition in a 0.5 kg h–1 FBCVD reactor, using ethylene as a carbon source. The carbon nanotube yield was shown to increase with an increase in synthesis temperature from 3.3% at 550°C to 87.6% at 900°C. At higher synthesis temperatures the quality of the nanotubes appeared to improve, although further experiments are required to quantify this within statistically significant limits.