What do Elizabethan cannons, your smartphone, #2 pencils, nuclear reactors, diamonds, and carbon nanotubes all have in common?
Graphite – that’s what. Without it, our modern world would cease to exist.
Humanity’s use of graphite is roughly in balance with its production. A million tonnes of natural graphite are mined per year (mainly in China), and another 95,000 tonnes or more of synthetic graphite are produced. About 1.1 million tonnes of graphite are consumed annually, the vast majority of it in Asia (generally in China).
This mineral is a really good electrical conductor, which makes it ideal for use in batteries and fuel cells. The lithium ion battery in a Nissan Leaf, for example, contains almost 40 kg of graphite.
In the 16th century, the Crown strictly controlled mining and production of the very pure graphite deposit in Borrowdale Parish, Cumbria, because its use in cannonball molds produced smoother, rounder shot that traveled further, giving the English Navy a distinct advantage.
The Elizabethans may have been the first to consider graphite a strategic mineral, but they were by no means the last.
In 1960, the United States Geological Survey defined (PDF) strategic graphite as “certain grades of lump and flake graphite for which the United States is largely or entirely dependent on sources abroad” (links added).
Today, the US makes over 100,000 tonnes of synthetic graphite yearly but it’s the world’s fourth largest importer of natural graphite.
Thanks to its high melting point (over 3600 degrees C) and chemical inertness, graphite is used today as a refractory material in steel production for crucibles, molds, refractory bricks, etc.
Oddly enough, it can also be used as a carbon additive to harden molten steel as a carbon additive, although it is soft enough to be mixed with clay and used as pencil “lead” in pencils.
In addition to its importance in steel production, graphite is valuable as a high-temperature lubricant as well as in the production of electric-motor brushes, friction materials, battery and fuel cells, and high-strength composites.
And let’s not forget pencils, which consume 7% of the world’s total production.
A very pure grade of synthetic graphite is used in nuclear reactors as a matrix for the uranium rods and also as a neutron moderator to sustain the reaction while maintaining control of the reaction.
Graphite and diamonds
Graphite – pure crystalline carbon – forms at the planet’s surface when geologic processes carbonize the remains of living organisms. Its high ignition point makes it difficult to burn, but graphite is considered the highest chemical form of coal.
Unless an asteroid or comet hits a graphite deposit on Earth, diamonds – which are also pure crystalline carbon – form in the high-temperature, high-pressure conditions deep within the planet.
No one knows for sure if the carbon down there is purely inorganic or if some of it came from organic carbon (probably graphite) that was carried down by the subduction of a tectonic plate.
In any case, the diamonds would stay buried forever if not for volcanoes, specifically, kimberlites. These deep-seated, violent eruptions carry them up to the surface.
Diamonds are unstable in the relatively low temperatures and pressures up here. Once they arrive, they start to turn back into graphite.
Luckily for us, that process is extremely slow.
Graphite and diamonds are both pure carbon, but they have different crystal structures.
Diamond’s carbon atoms all have very strong bonds and are arranged in three dimensions.
Graphite has the same strong carbon-carbon bonds, but its atoms are arranged in two-dimensional sheets that are only weakly bonded together.
Its 3D structure, for example, makes diamond one of the hardest minerals known and a good abrasive, while graphite’s 2D sheets make it one of the softest minerals and a good lubricant.
Composites, graphene, and carbon nanotubes
The picture changes when you roll graphite sheets up and twist them into threads to take advantage of those strong carbon-carbon atomic bonds.
Now the graphite will harden steel and can be used in high-strength composites to make cars, airplanes, sports equipment and the like.
And then there are nanotubes [(h) in this diagram].
Yes, technology has made it possible to roll up a graphite crystal. These tiny straw-shaped graphite crystals are even stronger than graphite composites, and also very flexible.
Graphene is basically a sheet of graphite that’s only 1 atom thick, and it is even stronger than composites.
You can peel graphene off of graphite with a piece of adhesive tape. However, it’s not all that easy to produce it industrially.
We definitely want to produce graphene. The thinnest material known, graphene is also the strongest. It conducts electricity and heat better than most materials.
There is so much news about graphene and carbon nanotubes, we’ll just wait and take an in-depth look at them next week.
About 70% of the world’s graphite comes from China. In the early 21st century, China closed many of its mines and slapped its graphite miners with an export licensing requirement, a 20% export duty and a 17% value-added tax.
Naturally, world production dropped, but prices didn’t rise. In fact, they dropped as much as 12%. This may have been due to the announcement of large deposits of graphite in Canada and the availability of graphite in Brazil and Madagascar.
Another factor in the price drop is that demand for synthetic graphite from large steel and iron producers, including the US, is high enough that it is cutting into the natural graphite market.
It looks like graphite production and demand are going to continue to remain more or less in balance for the foreseeable future, even if the production sites vary due to political and market forces. Graphite, one of the raw materials that keeps our high-tech society and its infrastructure going, is plentiful and extremely versatile.
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- Graphite. Amethyst Galleries
- Graphite (C) – Classifications, Properties and Applications of Graphite. Azom.com
- Graphite: Keeping up with demand. Mining Journal
- Graphite. New South Wales Department of Primary Industries
- Graphite – The Metal of the Future. Northern Graphite Corporation
- Graphite. US Geological Survey
- Graphite. Wikipedia
- Nuclear graphite. Wikipedia