11-08 :: August 2011

nanotimes News in Brief

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The nanofibers lean in different directions depending on where they are located in relation to the chromium grid, because the ions are being drawn to the grid and strike the catalysts at various angles. © NCSU

to create graphitic carbon nanofibers. The catalyst rides on the tip of the nanofiber that forms beneath it, like a rapidly growing pillar. The term graphitic means that the nanofibers have carbon atoms arran- ged in a hexagonal structure – like graphite.

One problem with growing carbon nanofibers is that the surface of the catalyst can become obstructed by a carbon film that blocks catalytic action, preventing further nanofibers growth. Here’s where those ions come in.

The ions being drawn to the chromium grid are moving very quickly, and they choose the shortest possible route to reach the negatively-charged metal.

In their rush to reach the grid, the ions often collide with the nickel catalysts, knocking off the excess car- bon – and allowing further nanofibers growth. Video of the process is available here.

Because the ions are being drawn to the chromi- um grid, the angle at which they strike the catalysts depends on where the catalyst is located relative to the grid. For example, if you are looking down at the grid, a catalyst just to the right of the grid will appear to be leaning right – because ions would have been striking the right side of the catalyst in an attempt to reach the grid. These nanofibers are still straight – they don’t curl up – they simply lean in one direc- tion. The bulk of the nanofibers, however, are both