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David Bradley ISSUE #62
February 2007
Take the Volcanic Fast-track to Nanotube Production

Igneous rock from the Mount Etna volcanic eruptions could be used to mass produce carbon nanotubes, according to researchers in Germany.

Carbon nanotubes and nanofibers have become indispensable to nanoscience since their early 1990s discovery. However, mass production of these materials in nanotechnology itself remains an obstacle to their widespread adoption. Now, Dang Sheng Su and his colleagues at the Fritz Haber Institute in Berlin have found they can use the particles of iron oxide found in igneous rock to help them deposit carbon nanotubes and fibers directly by reacting and condensing an organic gas on the surfaces of the tiny oxide particles from the gas phase.

Etna is the most active volcano in Europe, violently spewing out several million cubic meters of lava in its violent eruptions of 2002 and 2003. It is the highly porous nature of the cooled lava that Su and colleagues reasoned might provide a fertile surface on which to grow tiny carbon structures. They pulverize igneous rock and heat it to 700 Celsius under an atmosphere of hydrogen gas. This has the effect of reducing the nanoscopic particles of iron oxide to iron metal.

They then blast hydrogen and ethylene gas over the reduced powder. The iron particles catalyze the decomposition of the ethylene to elemental carbon, which then condenses, forming tiny fibers and hollow tubes. The main advantage of this new approach lies in the all too renewable and naturally occurring igneous rock. Moreover, there are no "wet" chemical reaction steps to carry out and it works at relatively moderate temperatures. Next step, applications.

Angew Chem Int Edn, 2007, in press; http://dx.doi.org/10.1002/anie.200604207