Metalwork - Materials - The Structure of Carbon
Diamonds are made up of carbon atoms. Up until recently they were considered to be the hardest material, and are used to cut most other materials. Graphite is another form of the element carbon. It rubs off easily on paper, which is why we use it to make pencil leads.
If diamonds and graphite are made out of the same element, why do they look so different and behave so differently? Let's look at their molecular structure :
To the left is an image of the crystalline structure of a diamond. The spheres represent carbon atoms; the lines connecting the atoms represent Chemical Bonds. Each carbon atom is at the center of a four-sided pyramid, (or tetrahedron), formed by the neighbouring carbon atoms to which it is bonded.
To the right is an image of a graphite crystal. A few carbon atoms are bonded vertically to those above and below, but most are only attached to neighbours in the same horizontal plane.
Do these drawings suggest a reason why diamonds are hard while graphite breaks apart easily? The answer has to do with how the carbon is bonded in the two materials or the structure of the materials. A massive amount of force can be absorbed by a diamond crystal because each bond is supported by many other bonds. If a force is applied in the horizontal direction to a graphite crystal there are very few bonds to absorb the force and so the layers will slip over each other, causing the graphite to break apart.
Materials scientists are interested in knowing how a material's macroscopic properties (hardness, resistance to extreme temperatures, electrical conductivity, etc.), are related to its atomic structure. This knowledge can be used to improve materials and develop new materials to meet specific needs. Proving the worth of these studies materials scientists at Lawrence Berkeley National Laboratory recently invented a new material that is harder than diamond. It may be used as an inexpensive substitute for diamonds or to carve diamonds into intricate shapes for use in electronic devices.
Scientists are also experimenting with a recently discovered carbon structure, called buckminsterfullerene ("fullerene" for short, or "buckyball" for fun). The buckyball is named after Buckminster Fuller, (who also invented the geodesic dome). One of the many interesting qualities of buckyballs is that atoms of other elements can be put inside the buckyball atomic structure creating all sorts of possibilities for new materials.