Understanding Graphene – Part 1
Graphene is to Graphite as a playing card is to the pack.
There, that’s the short version, if you’d like to know more read on…
The building blocks:
These graphene layers stack one on top of another to form graphite
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The properties of graphite and graphene:
The bonds between carbon atoms are strong within the layer but much weaker between layers. These layers slide over one another quite easily and can shear off. This is why graphite has been used as a lubricant and also helps understand how a graphite pencil leaves the characteristic line on a sheet of paper.
This doesn’t explain some of the other properties that graphite and graphene display, to do that we need go a little further into the atomic structure and explore a mystery.
There is a puzzle at the heart of graphene; each carbon atom should be connected to four other atoms. These connections are made by shared electrons and called bonds. Look closely at the graphene layer and you’ll see that there are only three bonds. Where has the fourth bond gone?
The fourth bond is actually present, just not in the form you might expect. The fourth bond projects upward and downward from the plane of the layer. It becomes merged with the others in the ring structure creating an electron cloud called a pi system.
This electron cloud above each ring further merges with all the other rings in the graphene layer creating a continuous π orbital that stretches over the whole graphene sheet.
This free movement of electrons through the graphene layer is why it conducts electricity better than other materials for example electrons can move 100 times faster in graphene than the silicon used in computer chips.
In graphite the graphene is not continuous as it is broken up into crystal flakes, within these flakes are the layers of graphene. This means that while graphite does conduct electricity it is not as good an electrical conductor as graphene. Graphene has been reported to be 5000 times better than graphite as an electrical conductor.
When does graphite become graphene?
The obvious answer is that graphene is a single layer material and graphite is a multiple layer material. Things are not quite that simple. A global market has emerged that is selling multilayer graphene. Investorintel has been analysing this market and the report will be available in the near future.
The Royal Society of Chemistry reports that it takes about 10 layers before the electronic properties revert to those of graphite. This would be a clear place to draw the line between graphite and graphene and help understand the products out there in the market.
At the time of writing in 2016, in the global marketplace, graphene can be bought in kilogram quantities. This is usually as graphene powder or slurry of multi layer nano-flakes in a liquid in varying levels of quality.
True graphene is available in millimetre or centimetre scale quantities usually attached to a copper or silicon surface. As such true graphene is more a product for research organisations than an industrial raw material.
The reason why true graphene is available in such small quantities is because it is rather hard to create. There are a variety of methods used to manufacture graphene these, dear Investorintel reader, are the subject of the next column.
Adrian Nixon began his career as a scientist and is a Chartered Chemist and Member of the Royal Society of Chemistry. As a scientist and ... <Read more about Adrian Nixon>