Tubular carbon nanostructures produced by tunneling of cobalt nanoparticles in carbon fibers

Tubular carbon nanostructures have been produced by the tunneling of cobalt nanoparticles in carbon fibers that are derived from electrospun polyacrylonitrile (PAN) fibers. During the annealing in a vacuum up to 1400 °C, carbonization takes place to the cobalt-doped PAN fibers, causing these fibers to transform to a composite of cobalt nanoparticles and carbon fibers. Cobalt nanoparticles embedded in the carbon fibers start tunneling in these fibers, thus producing various tubular carbon nanostructures. During the tunneling, carbon atoms confronted with the cobalt nanoparticles diffuse into these particles, which later precipitate from them and leave a tubular structure behind.

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► Carbon tubules are produced by tunneling of cobalt nanoparticles in carbon fibers.
► Driving force is high chemical potential of amorphous carbon relative to graphite.
► Cobalt nanoparticles are from cobalt oxide reduced by carbon during heat treatment.