New faster method for making large scale, high quality graphene
Regular InvestorIntel readers will know I have a particular interest in the manufacturing of graphene. Things are moving fast in the world of this new two-dimensional (2D) material. I’ll bring you up to speed, read on…
Current state of the art of graphene manufacturing
At present commercial quantities (kilogrammes and tonnes) of graphene are made from graphite usually by the top down method. These are available as powders and liquids that can be used as additives in other products such as rubber and carbon fibre composites.
To realise the full potential of graphene it really needs to be manufactured as large-scale sheets. This is beyond the state of the art of manufacturing at the moment, but things are moving fast in the research labs around the world.
The Chemical Vapour Deposition (CVD) method is another way to make graphene. This is called the bottom up method because it assembles the graphene sheet atom by atom. The CVD process forms graphene on the surface of copper metal. This is currently the best bet for making large-scale sheets of graphene. However this process is still in the research lab as there are some fundamental problems to be overcome.
The main problems for making graphene by the CVD method
Quality and speed sum up these problems. On the quality side the main source of the problem is that graphene grows on the surface of the metal simultaneously from many points. These points grow into islands that create defects in the sheet where they join. A sheet of graphene formed in this way is said to be polycrystalline. Think of a sheet of fabric made from many pieces of the same material loosely stitched together and you’ll get the idea.
The ultimate goal is to make a flawless sheet of material and this is called single crystal graphene.
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The other problem is the speed of manufacturing. Current CVD methods grow graphene at a speed of 50 microns per minute. This probably won’t mean much, so think of making a square metre of graphene. We used a square metre as the basis for measuring the scale of sheet graphene manufacturing in a previous column. (One square metre = a hammock index of 0). With a few assumptions, at this speed it would take two weeks to produce just one square metre of poor quality product.
Hardly promising as the foundation of a new industrial revolution.
Then, last week a team in China published a rather interesting paper…
Liam Critchley at the National Graphene Association (NGA) brought to my attention that the clever ladies and gentlemen, at Peking University and the Ulsan National Institute of Science and Technology (UNIST) in Korea, announced a new development. Their article was titled ‘Ultrafast epitaxial growth of metre-sized single-crystal graphene on industrial Cu foil’ Not perhaps everyone’s idea of a riveting read, but it got my attention. Thanks Liam.
What the Chinese have done is proved graphene can be made faster than thought possible and, at the same time, with much higher quality.
The paper is not the easiest of reads; let me explain what they have actually done:
The team started with a piece of solid copper 5×50 cm (250 square centimetres) they have grown a layer of graphene on this in 20 minutes. This is the fastest anyone has produced graphene. They also claim to have grown the graphene as a single crystal on this material. This means it is a very high quality layer of graphene one atom thick.
There are a number of implications, let’s focus on two:
You’ll recall I calculated it would take 14 days to produce one square metre of graphene. This work shows it could now be done in 13 hours. This is twenty six times faster than the previous fastest method.
This implies we can get even faster speeds. I’ll make a guess that people will start comparing graphene manufacturing with Moore’s law for making computer chips.
Most current methods make polycrystalline graphene which is poor quality, think of lots of separate bits loosely stuck together to make a flat sheet. This Chinese work shows they have produced something close to single crystal graphene, which is the highest quality – one continuous sheet of graphene with no defects.
All exciting stuff, but let’s put this in to perspective.
There is a danger of marketing hype at play here. The team describe this method as ultrafast. Remember, in this context ultrafast would mean making something like a square metre in thirteen hours instead of fourteen days. Good progress but still painfully slow for a viable manufacturing process. Also consider that this graphene sheet is stuck to the metal copper foil and has to be removed. However keep watching developments because in the world of graphene this really is a big step forward.
I’ll keep watching this fast moving space for you; expect further reports on the manufacturing of this wonder material.
For now, in terms of speed, it is China 26: Rest of the World 1.
Adrian Nixon is a Senior Editor at InvestorIntel. He began his career as a scientist and is a Chartered Chemist and Member of the Royal ... <Read more about Adrian Nixon>