There are three different allotropes (forms) of carbon that are commonly known. There are amorphous carbon, graphite, and diamond. There are also several fullerenes (substances made completely of carbon), which include carbon nanotubes and carbon Nano buds and Nano fibers. These things were once considered rare, but now are made commonly for use in research. There are also less well know and hard to find types of allotropes such as carbon nanofoam and glassy carbon, among others.
Amorphous carbon is a set of carbon atoms in an irregular, “glassy” state which is the basics of graphite except for the fact that it is not in a crystal-like structure at the Nano level. Its main form is a powdery substance and is the main substance in things like charcoal, soot and activated carbon (a form of carbon that has small holes that increase the surface area and make it easier for it to absorb other substances or chemical reactions).
Graphite is formed when carbon is at normal pressures. When it takes the form of graphite, the atoms of the carbon are bonded triagonally to three others in a “plane composed of fused hexagonal rings”. This leaves a network of 2-dimentional atoms and these sheets of flat carbon atoms are stacked and bond together. This is what makes carbon so soft and malleable.
The diamond form of carbon is formed when carbon is put under high pressures. Diamond has almost twice the density of graphite because of its compacted form. In diamonds, the atoms are bonded tetrahedrally to four other atoms, which makes it a “3-dimenstional network of puckered six-membered rings of atoms”. Silicon and germanium both have the same cubic structure as diamond. Also, because of the strength of the carbon-to-carbon bonds, diamond is one of the hardest naturally occurring substances when it comes to resistance to scratching. Under normal conditions, diamonds are thermodynamically unstable and will transform to graphite. The transition to graphite from a diamond state at room temperature is so slow that it is unnoticeable.
Fullerenes have a structure very similar structure to graphite, but instead of hexagonal bonding, they also contain pentagons and sometimes heptagons. This will turn the sheet of atoms into spheres, ellipses or cylinders. The fullerenes haven’t been fully analyzed yet. There is a lot of research to go before we fully understand what they can do. Buckyballs, a type of fullerenes, are large molecules formed out of carbon-bonded triagonally, which forms the spheroids (such as the buckminsterfullerene which is soccer ball shaped). Carbon nanotubes are bonded in also triagonally but form a cylinder shape.
http://en.wikipedia.org/wiki/Carbon,
October 30, 2012, 1:17 pm
November 1, 2012 1:07 pm
November 6, 2012 1:02 pm