Industrial production of multiwalled carbon nanotubes

Carbon Nanotubes are currently being synthesized by different methods. The methods differ largely by the achievable space‐time yield, amorphous carbon content and carbon purity. High space‐time yields can only be achieved by CVD processes. Though usually low contents of amorphous carbon are observed in CVD processes, C‐purity is generally decreased due to catalyst residues. Bayer Technology Services has developed a high‐yield process for multi‐walled carbon nanotubes (MWNT, trade name Baytubes ® ) based on a CCVD process starting from light hydrocarbons. The produced Baytubes ® are characterized by a very high graphite content and an excellent purity (carbon content >95 wt%). Due to their high purity and quality, Baytubes ® can be employed directly in further processing. The Baytubes ® were incorporated into different polymers and also into liquids. The primary feature for good mechanical and electrical properties of the polymer composites is a full dispersion of the CNT in the polymer matrix. TEM analysis is an important method to investigate the CNT dispersion on the nanometer scale. But it is also necessary to combine different methods to ensure a good and constant dispersion quality. Thus, different analysis methods were developed by BTS during product development. Process scale‐up is under way and a nominal production capacity of 60 tons per year has already been commissioned. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)