It’s the thinnest, strongest material known to exist. It’s light, flexible, transparent and is one of the best conductors of heat and electricity ever measured. Its possible applications are seemingly endless, and include everything from making smart roads to targeted cancer treatment. And it is present at the tip of a pencil. This is graphene.
Graphene is a molecule and an allotrope of carbon. Essentially, that means it’s a form that carbon can take. Another allotrope of carbon is a diamond. In the case of graphene, it consists of a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice.
The question is, how is graphene produced? And how is graphene made from graphite? Let’s find out.
Discovery of Graphene
Graphene was first discovered in 2004, by scientists André Geim and Kostya Novoselov at the University of Manchester. Actually, that’s not quite accurate. The existence of graphene was already known, but Geim and Novoselov learned how to extract or isolate it. Essentially, they discovered how graphene is made.
So how did they do it? Well, they were playing around with some experimental science, something they did outside their usual work. In this case, they used sticky tape to remove flakes from a lump of graphite. Noticing that they could make the flakes ever thinner, they kept going. Until they made flakes just one atom thick. These tiny fragments were graphene.
It was a massive breakthrough. The properties of graphene are extraordinary. It’s flexible enough to stretch an extra 20% of its original size, its thickness is that of a single atom and yet it’s ten times stronger than steel. Added to that, it is transparent and an excellent conductor of heat and electricity.
In 2010, Geim and Novoselov received the Nobel Prize in Physics for their work. Graphene was hailed as a wonder material with potential applications in everything from construction and electronics to medicine and farming. However, to fulfil its promise, graphene would have to be manufactured on an industrial scale. So, how is graphene manufactured?
How is Graphene Made from Graphite?
As discovered by the scientists at Manchester University, graphene can be made from graphite through a process known as mechanical graphite production. As for how is graphene produced on a larger scale, there are several methods, with more being innovated all the time. In this article, we’ll explore both mechanical graphene production, and chemical vapour deposition.
Mechanical Graphene Production
Mechanical graphene production is a way of exfoliating graphite. This process involves using strong adhesive tape to peel off thin layers of graphite, thus creating graphene.
But using lots of adhesive to peel off graphene flakes from a vat of HB pencils is not scalable. So how is graphene produced in other ways?
Chemical Vapour Deposition
Chemical Vapour Deposition, or CVD, is a way of growing graphene on a substrate like a copper plate or nickel foil. This method of how graphene is made is done using carbon atoms from a gas like methane.
The substrate is placed in a chamber and heated to a high temperature. Then, the gas containing carbon is introduced. The carbon atoms in the gas deposit onto the substrate, forming a layer of graphene. This produces what is called ‘one layer graphene’.
There are several issues with this, not least how to separate the graphene from the substrate. One method is to ‘line’ the substrate with the polymer parylene before growing the graphene on it. The parylene layer is said to make it easier to remove the graphene once it grows, without interrupting its connection with the copper, much like using a baking sheet to make cookies.
This method is useful for creating large areas of graphene, but it has some drawbacks. The first is that it can be difficult to control the thickness of the graphene. The second is that this process can introduce defects into the material.
The final answer to ‘how is graphene manufactured’ returns to using graphite. So, how is graphene made from graphite in this method?
Strong acid can be used to disrupt the molecular bonds in graphite to produce graphite oxide which, when stirred, becomes graphene oxide. This can be altered to make reduced graphene oxide (RGO). RGO is close to but not pure graphene. This method is known as chemical exfoliation. There is now a proposed related method called electrochemical exfoliation.
This involves placing pure graphite ore in a container with a chemical solution like ammonium sulphate. Electrodes are placed in the solution, delivering a current which propels ions from the solution in between the graphite’s layers. This creates bubbles in the liquid which in turn separate the graphite layers, breaking them down into graphene oxide. Again, this isn’t quite graphene and doesn’t have all of its exceptional qualities. However, it can be used as an additive to provide other materials with some of those qualities.
How Graphene is Produced
It seems that the only current answer to the question ‘how is graphene made from graphite’ is the mechanical process. All other methods developed so far have produced compromised forms. The good news is, processes to make graphene are being developed all the time. But until we have the answer to ‘how is graphene manufactured’, we’ll have to wait to see this wonder material in wider use.