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Carbon nanotubes
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Several types of carbon
Several types of carbon
Diamond, a transparent mineral
Chemical bonds between atoms are strong, and the tetrahedral symmetry is that of a dense and isotropic material. It is an electrical insulator, and the best refractory and thermal conductor known.
Graphite, a black and friable mineral
Its structure consists of layers stacked together, each formed of regular hexagons of carbon atoms. This structure is 1/3rd weaker than that of diamond, making graphite an anisotropic and virtually two-dimensional solid. The layers are connected together by weak forces, and slip easily over one another. It is a semi-metal within the layer, with little conductivity in the other direction.
Fullerene, or Buckminsterfullerene
This molecule consists of 60 carbon atoms placed at the top of a regular polyhedron whose sides are hexagons or pentagons. Fullerene is electrophilic. It features high resistivity (approximately 1014 Ω/cm).
Fullerene has a few applications, including microporous filters, sample supports for electronic microscopes, lubricants, etc.
Carbon nanotubes
Carbon nanotubes are a closed pipe-shaped material consisting of crystallized carbon. The length of the nanotubes can reach several microns, while their diameter ranges from 1 nm to 60 nm.
The nanotube is represented by a graphene sheet wrapped or coiled based on a reference axis and direction. The helix angle (helicity) is variable, ranging from 0° to 30°. Nanotubes are closed by distortion of the hexagons, and by the introduction of pentagons in the nanotube structure.
There are several types of nanotubes. Nanotubes are structured into single walls (Single Wall Nano Tubes, SWNTs) or multi walls (Multi Wall Nano Tubes, MWNTs).
The tubes nest within one another, with the distance between the walls close to the distance between two graphite planes (0.34 nm). Both structures are the result of different synthesis conditions.
There are several types of nanotubes
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