HOUSTON -- (July 27, 2009) -- New video showing the atom-by-atom growth of carbon nanotubes reveals they rotate as they grow, much like the halting motion of a mechanical clock's second hand. Published online this month by researchers at France's Universit Lyon1/CNRS and Houston's Rice University, the research provides the first experimental evidence of how individual carbon atoms are added to growing nanotubes.
"The key issue for realizing the potential of carbon nanotubes has always been better control of their growth," said team lead Stephen Purcell of the Universit Lyon1/CNRS. "Our findings offer new insights for better measurement, modeling and control of nanotube growth."
Carbon nanotubes are long, hollow cylinders of pure carbon. They are hair-like in shape but are about 100,000 times smaller than human hair. They are also about six times stronger than steel, conduct electricity as well as copper and are almost impervious to radiation and chemical destruction. As a result, scientists are keen to use them in superstrong, "smart" materials, but they need to better understand how to produce them.
"The images from Dr. Purcell's lab show the atom-by-atom 'self assembly' of a nanotube," said Rice co-author Boris Yakobson, professor in mechanical engineering and materials science and of chemistry. "The video offers compelling evidence of the rotational motion that accompanies nanotube growth. It brings to mind Galileo's famous quote, 'And yet, it does turn.'"
In February, Yakobson offered a new theory suggesting that nanotubes grow like tiny, woven tapestries, with new atoms attaching to twisting atomic threads. The new video appears to support the theory, indicating that atoms are added in pairs as the tube spins and grows.
To create the images, Purcell's team at LPMCN (Laboratoire de Physique de la Matire Condense et Nanostructures) used a field emission microscope (FEM). A few atoms of metal catalyst were place
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