Before we examine graphene production and all the related processes, it is beneficial to briefly touch on the unusual properties of graphene.
Graphene is a two-dimensional sheet of carbon atoms. The atoms are arranged in hexagonal lattices, like benzene rings, and since the layer is just one atom-thick, the actual thickness of the atoms is for all purposes negligible.
Despite being isolated decades later, graphene was first theoretically conceived in 1947. It was proposed that graphite consists of stacks of 2D carbon atom-layers.
In 1984, it was predicted that a single layer of carbon atoms would be electro-conductive. Finally, in 1987, this single layer was coined as graphene.
Ever since 1987, scientists were trying to create graphene crystals in laboratory conditions. However, the strong forces acting between the surface and the crystal inhibited any potential for graphene creation or experimental measurement.
Since 1987, it took the scientific almost 20 years to successfully create a single graphene sheet. As with other breakthroughs, this was also an accident.
Sir Andre Geim and Sir Kostya Novoselov had a habit of performing random experiments in their spare time. They would choose topics which didn’t warrant enough space in day-to-day research; or would simply suggest unusual directions off the cuff. One evening in 2004, they were experimenting with iteratively removing layers of carbon atoms from graphene by tape. What they ended up with was the first single atom-thick layer of carbon atoms, graphene.
In 2010, both scientists received a Nobel Prize for their discovery.
Geim’s and Novoselov’s exfoliation method allowed laboratories to start creating graphene. The material had properties bordering on miraculous and it was difficult to curb the build-up of enthusiasm. Graphene turned out to be superconductive, super-strong, flexible, transparent, biocompatible, and light.
Emergence of new methods
While exfoliation allowed for the production of graphene in laboratory conditions, it was also costly. For this reason, companies that wished to capitalize of graphene’s future migration into the consumer marked had to find more economically viable methods.
The new methods allow for the production of graphene, as well as graphene oxide and allotropes (nano-tubes and fullerenes).
Chemical vapor deposition
One of the most prospective methods of graphene production is chemical vapor deposition. In this type of production, silicon carbide is heated under low pressure; which reduces the material into graphene. The graphene stacks on top of the substrate in multi-layered accumulations held together by Van der Waals forces.
The detonation technique, just as the discovery itself, was also found by accident. A team of researchers carried out an experiment that strived to create aerosol soot gel by detonating ethylene or acetylene with oxygen. When they collected the end product from the chamber, they found out it was graphene and not gel. The benefit of the detonation technique is its low demand on technology (detonation chamber and spark plug), energies (spark), and chemicals (simple hydrocarbon gasses and oxygen). Furthermore, the method produces grams of graphene instead of the usual milligrams produced by other methods.
Further new methods
New approaches to creating graphene continue to appear as the material gathers more attention. It is synthesized from organic sources such as oils or a product of bacteria; or made by carbon dioxide reduction. These methods are still in their infancy and it will take time to assess their benefits.
What is the situation today?
The methods of graphene production can vary substantially in terms of time (from minutes to hours), volumes, purity, and costs. At this time, there are over 60 sources of graphene, offering it under different conditions. The field proves stimulating for new businesses, as the high percentage of the sources are start-ups and new companies. The big players adopted a more careful approach and most likely are waiting to see which production method will prove itself.