From HomoExcelsior

Fullerene related structures made of graphene cylinders closed at either end with caps containing pentagonal rings.

Carbon nanotubes are rolled sheets of graphite just nanometres in diameter. The electronic properties of a tube : metallic, semiconducting or a combination of the two : depends on whether it is made from one or many layers of graphite, and on the angle at which the sheets are rolled. The tubes are called 'zigzag' or 'armchair' depending on the angle of roll.

Carbon nanotubes can be used to make constructions of incredible size due to their strength (extremely high Young's Modulus) and ease of connectivity. See megascale engineering and beanstalk.

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