Carbon Molecules Turn Into "Buckyballs" Because of High Heat

Carbon buckyballs, no bigger than a strand of DNA, were first discovered in 1985 and their formation process has remained a mystery, but now scientists at Sandia National Laboratory and Rice University have discovered the mechanism that produces carbon buckyballs from carbon graphite.

Metals research is of prime importance in the 21 century because new understandings of the properties of metals are critical to furthering space exploration, advanced technologies, environmental concerns and human health.

Buckyballs are unstable parts of a sheet, or layer, of carbon graphite, and when the unstable sheet of carbon is exposed to heat, the buckyballs form. The graphite, a black form of carbon that conducts electricity and is a naturally occurring mineral, sheds the loose threads or chains of carbon that contribute to the instability. After these are shed, the round buckyball remains.

But if the heat continues to be present, the buckyballs shrink up and vanish altogether. Buckyballs both form and vanish at high temperatures. The prominent theory for their occurrence is called the "hot giant" theory. It suggests that the myriad carbon atoms that are assembled in a sheet are effected by the heat in such a way that the sheets, or layers, are distorted in shape and the atoms collide or collect together. This collection keeps distorting and shedding until all that is left is a perfect sphere. This perfect sphere can also shed away and vanish if heat continues to be applied. The scientists call this distorting and shrinking process "shrink wrapping". Normal shrink wrapping that we encounter every day is a similarly caused shrinking of size as a result of the application of heat.

The breakthrough that allowed the discovery of this process came about when Jianyu Huang of Sandia National Laboratory developed a remarkable "controllable heat bath inside a 10-nanometer-wide nanotube," as explained by co-author Boris Yakobson, who is a professor of mechanical engineering and materials science at Rice University.

Huang then used an electron microscope (TEM) to obtain high-resolution images of the carbon graphite, situated in the heat bath in the nanotube, responding to the heat. Fullerenes are carbon forms that are made up of hundreds of carbon atoms that form giant spheres that exist within graphite. Huang's TEM images show these fullerenes shrinking under heat until the perfectly spherical buckyball is left, and then it vanishes too.

This research is currently available online and will later be published in the Physical Review Letters (PRL), having been distinguished by being chosen as an "Editor's Suggestion" research paper.

The two other co-authors are Feng Ding, a research scientist, and Kun Jiao, a postgraduate research student. Both are affiliated with Rice University.

A video of the fullerenes shrink wrapping into buckyballs in the carbon graphite sheet is available online.

"Video shows buckyballs form by 'shrink wrapping': Experiments, simulations reveal birth secret of tiny carbon spheres," Rice University.