Apr 15, 2008
One-step method simplifies CNT growth
A one-step technique for synthesizing aligned arrays of multiwalled carbon nanotubes (MWCNTs) could soon rival popular production methods, such as CVD and PECVD, thanks to its affordability and ease of operation. Based on pyrolysis and developed by members of the Indian Institute of Science (IISc) in Bangalore, the technique eliminates much of the complex and expensive machinery used today and instead requires just a quartz tube, a single-stage furnace and a rubber bladder.
"We believe that our method will greatly reduce the production cost of carbon nanotubes," Karuna Kar Nanda of the IISc's Materials Research Centre told nanotechweb.org. "The technique does not require any gas flow or substrate preparation, which also improves the production time."
To synthesize their nanotube arrays, the scientists placed 18 mg of catalyst (ferrocene) and 2 ml of carbon source material (either xylene, cyclohexane, camphor, hexane, benzene or toluene) into a quartz tube. Closed at one end, the reaction vessel measures 10 mm in diameter and 700 mm in length. Next, the whole assembly was placed inside a single-stage furnace that was raised to 700 °C for 30 minutes and then cooled to room temperature. A rubber bladder at the open end of the quartz tube collected any residual reacted gases.
As well as making conventional MWCNTs, the group can produce bamboo-shaped CNTs by using pyridine as the carbon source material. These nanotubes contain many separated hollow compartments, which suit applications such as nanoelectronics, biosensors, gas storage and optical communications. It is thought that the presence of nitrogen in the carbon source material is responsible for the structure's unusual shape.
The team's production method delivers around 54 mg of MWCNTs after using standard purification treatments to remove amorphous carbon material and catalyst particles.
"Currently, we are looking to scale up our process to produce low-cost carbon nanostructures in large quantities," added Pitamber Mahanandia of the IISc's Department of Physics. "We are interested in teaming up with industrial, and research and development partners and will be approaching them in due course."
The researchers presented their work in Nanotechnology.
About the author
James Tyrrell is editor of nanotechweb.org.