For a long time only two main types of carbon were known, namely graphite and diamond. A third carbon crystalline type has been discovered, however: the fullerenes. They compose the basis of the new technologies of the 21st century and, paradoxically, this molecule group, incidentally also found in cosmic dust, is no doubt one of the oldest molecules in the universe. Let us briefly recall that pure carbon comes in different forms. To categorise them, it may be useful to remember that there are four available links in the carbon atom.

If the carbon is connected to its neighbours by four simple links, forming a coordination known as tetrahedral, there is of course the diamond, but also a hexagonal shape, the Lonsdaleite. This is for the crystalline components, without forgetting that there are also amorphous varieties, and more specifically the adamantine carbon, especially resulting from the CVD (Chemical Vapour Deposition) method which has a great deal of applications in thin layers, thanks to it being very hard indeed. If carbon is connected to its neighbours by two simple links and one dual link, we get any and all the products of the graphite group. They are built by the piling up of graphene insets, a surface consisting in adjacent hexagonal circles of six carbon atoms. In other words, graphite consists in different layers, one on top of the other, in two-dimensional structures: the layers slide on top of each other without any problems, which gives graphite its exceptional lubricating property.
Last, if carbon is connected to its neighbours by a simple link and a triple link, a far more rare case, we are in the carbine group, which includes the chaoite found included in meteorites.
The discovery of the fullerenes dates back to 1985. A team of American and English researchers – Robert F. Curl and Richard E. Smalley, from Rice University in Houston, as well as Harold W.Kroto, from the University of Sussex – have a layer of graphite evaporate in a helium atmosphere with a laser. When the carbon heats up to steam up to 8,000°C, the scientists detect a mysterious unknown carbon form composed of exactly 60 atoms.
The discovery of such brand new atom heaps will be awarded the Nobel Prize in Chemistry in 1996. The researchers name this 60 carbon atoms molecule “buckminsterfullerene” or “Bucky ball” as it is referred to by those ‘close friends’: this name draws its inspiration in the round shape construction (geodesic domes) which look somewhat like a foot ball as designed by Buckminster Fuller, the architect cum engineer. The molecule, just like the building, consists in a composition of hexagons and pentagons networks, the pentagons making curving possible.
Later on higher type fullerenes were looked into, especially the C70 fullerene. Such studies have progressively led to the discovery and study of the carbon nanotubes. Revolutionary applications of this molecule are on going. As early as 1999, Professor J. Van Landuyt, from the University of Antwerp, had forecast that the fullerene applications would be very varied: they go from superconductivity to the treatment of cancers. Indeed, the carbon 60 reveals something of a cage, which may be filled. Other atoms may be introduced in it such as for instance radioactive atoms, which are used in the treatments of cancers. The cage may also be filled with substances having electronic properties: and so a new generation of electric batteries is being worked on. In 1991 the Japanese Sumio Lijma discovers surprising carbon fibres in the fullerenes and he calls them “nanotubes”. Today many processes enable to get such nanotubes. Resistant and hard, this allotropic form of carbon offers very many application possibilities. The considerable mechanical resistance and the lightness of the nanotubes (100 times more resistant than steel and six times lighter) make them the ideal materials for robust structures which need to be light as well such as, for instance, composites for aircraft structures and electronics for instrument panels. Whether woven, or twisted, they are part of far more resistant products for ropes, cables, safety belts, etc. They can absorb considerable impacts and are nevertheless light, so they are ideal for bulletproof vests, armour plating, bumpers. They may be used in ultra resistant layers or coating. Since they are small and good conductors, a very small quantity of such materials may turn any material, such as polymers, into a conducting one. They may be distorted with a current, so the nanotubes are used as bases for small mechanical tools in integrated circuits: the NEMS (Nano Electro Mechanical Systems). Since they are also good conductors of heat (something around 20 times better than copper), they might contribute to the building of extraordinarily efficient heat dissipaters and sinks. In computer science, they are non-volatile memories of a considerable capacity. Finally, a property which is less often discussed in public, they are microwave absorbers and therefore, they could be used for stealth devices which are of interest for the military.
The University of Bayreuth has submitted carbon 60 to considerable pressures, at 20 GPa and at 2,500°C, under a 5,000 ton press, creating a new form referred to as “aggregated diamond Nano rods (ADNR)” The ANDR has a different structure, from 5 to 20 nanometres in diameter and 1 micron in length, which makes it resistant to 491 gigapascales as compared to 442 gigapascales “only” for natural diamonds. The geology Professor, Tetsuo Irifune, and his team from the University of Ehime in Japan, has created a poly-crystalline diamond from carbon. They brought the graphite to temperatures between 1,800°C and 2,500°C instead of 1,500°C and 1,800°C, and to pressures between 150,000 and 250,000 atmospheres. The poly-crystalline diamonds (PCD) between1 and 3mm are thought to be twice as resistant as the traditional synthetic diamond. Nanotechnology is only in its first stages and the 21st century will live an actual revolution in several sectors. The diamond family will always surprise us indeed... .