08 Oct

Carbon Nanotube

How do you make a carbon nanotube?  One way is by chemical vapor deposition in a tube furnace.  Metal catalyst particles such as iron, cobalt, or nickle, or a combination are heated in the furnace to 700°C (1300°F).  A process gas such as hydrogen or ammonia is passed across the particles along with a carbon containing gas, e.g.,  acetylene, ethylene, methane. . .  The nanotubes grow at the site of the metal catalyst particles.

Much research has been done to find a way to deposit carbon nanotubes on various substrates.  Recently researchers at MIT found an elegant and simple method.  The carbon nanotubes are compressed into lead for a pencil.  Carbon nanotubes can be deposited on a substrate merely by drawing a line with the pencil.  One application is a portable compact gas sensor.  A gas sensor can be devised by drawing a carbon nanotube line on paper imprinted with tiny gold electrodes; the line of carbon nanotubes act as a resistor.  If the current across the carbon nanotube pencil line changes it means a gas has bound to the nanotubes.  The sensors give consistent results even when the lines drawn are not regular.

Robin Prymula

Massachusetts Institute of Technology. “Drawing a line, with carbon nanotubes: New low-cost, durable carbon nanotube sensors can be etched with mechanical pencils.” ScienceDaily, 9 Oct. 2012. Web. 10 Oct. 2012.