Goodbye Summer, Hello Autumn
As August comes to end so do the summer holidays. The sun, sea and sand have come and gone, and now everyone is turning their attention to back to school – yay! For most of us, the week before school can only mean one thing – shopping! New shoes, new trousers, new shirts are first on the list, followed by bags, books and stationery.
One key item every student should have is the humble pencil! However, many of us mistakenly refer to the marking part of a pencil as lead! Now, lead may be a dull, soft looking material, but the fact it’s highly toxic means you definitely don’t want it in your pencil (and you certainly don’t want to be chewing that pencil!).
Can You C Where This Is Going?
The material used in pencils is graphite. But, despite it’s dull appearance and rather boring use, graphite is fascinating, and has a rather famous sibling.
You would think that diamonds and graphite could not be more different. One is a sparking, beautiful gem, highly valued, very expensive and used in jewellery, whereas the other is dull, soft, cheap and found in pencils. Despite their different looks, both diamond and graphite are made from the exact same thing, lots and lots of carbon atoms!
Diamond and graphite are allotropes of carbon, different structures of the same element.
Would You Like Your Carbon Layered or Tetrahedral?
So, how can two materials that seem so different contain exactly the same thing? Well, this all has to do with how the arrangement and bonding of the carbon atoms!
In diamond, each carbon atom bonds to another four carbon atoms. This creates a large tetrahedral structure that is very rigid. As a result, diamond is very hard and has a very high melting point.
However, in graphite each carbon atom bonds with only three other carbon atoms. This forms large hexagonal sheets that are layered on top of each other. These layers can move over each other, making graphite soft and slippery.
There are even more things we can do with these sheets of carbon, mind you… We could take one individual sheet (by sticking one to a piece of sticky tape – highly technical stuff, this) and roll it up into a tube. We call these carbon nanotubes!
Or we could roll a sheet into a sphere to make a big carbon ball – a Bucky Ball!
A Carbon Conductor
The slight difference in the structure of diamond and graphite leads to one very important difference: electrical conductivity. Diamond does not conduct electricity, but graphite does. Because of this, graphite has a use in electrodes for batteries. It is highly likely that the device you are reading this on contains graphite in the battery!
Diamonds Are Not Forever…
It’s worth noting that from an energy point of view, graphite is more stable than diamond. So, if given the chance, diamond would much rather be graphite. However, the energy needed to convert diamond to graphite is very large and so does not happen easily.
The Age of Graphite
There is evidence of graphite use from thousands of years ago where, unsurprisingly, it found use in drawing and decorating. During this time, it became known as black lead, which is why many people often refer to pencil lead. Eventually, it was given the name graphite, meaning “writing stone”.
In the 1500s a large supply of graphite was found in the North of England where it was used in the making of cannonballs. By the 19th Century, graphite has many uses, including in the production of pencils. Apart from this, graphite had uses in polishes, lubricants and paints.
A Road to Graphite
So far, most of the graphite in use was natural. In the 1890s, scientists had discovered two processes for making graphite artificially. The more famous, the Acheson method, involves making silicon carbide and then overheating it. This removes the silicon, leaving pure graphite!
There was been a lot of recent research into the thermal decomposition of methane. The hope it that this process is green, environmentally friendly, low cost and a great way to produce both graphite and hydrogen.
The Plight of Graphite
Apart from pencils and batteries, what other uses does graphite have?
Graphite can be ground into a powder and applied to surfaces. Since the sheets of carbon atoms can slide past each other so easily, this makes for a fantastic lubricant. Many industries rely on graphite lubrication to work effectively.
You may also find graphite in nuclear reactors where they can absorb neutrons and help control the reactions.
C, C, and C
Summer might be over and school may be beginning, but next time someone talks about pencil lead, you can tell them that lead is actually graphite. What’s even more amazing is that graphite is made from the exact same stuff as diamonds – carbon!
It’s not just the old technology of pencils which contain graphite. Its use in batteries mean that many of the electrical gadgets we use also contain graphite.
Diamonds might well be a symbol of wealth and riches, but we would all be a little bit poorer without graphite!