Science Interviews


Mon, 10th Aug 2015

What is graphene?

James Baker, National Graphene Centre

Listen Now    Download as mp3 from the show Getting to grips with graphene

5 years ago, Manchester University scientists Andre Geim and Konstantin Novoselov Making graphene with sticky tapewon the Nobel prize for extracting graphene. They did this using nothing more complicated than sticky tape and a lump of graphite - exactly as you get in your pencil. What they found was certainly a suprise. Graphene is 300 times stronger than steel; so thin you can see through it, and if you covered an entire football field with it, it would still weigh less than a gram. But what actually is this remarkable material, and why is it so special? James Baker explained to Chris Smith...

Chris - Iíve painted a picture of graphene, so far, as resembling chicken wire in some respects. But if we were to go in with a really, really powerful microscope, what would we see? What does it look like?

James - Graphene is a single atomic layer of carbon, two-dimensional material. So, occasionally, people talk about 2D material and actually graphene now is one of a number of over 2-dimensional materials that are now being looked at by the scientists. So, it is, if you like, a hexagonal structure. The chicken wire is a very good description and at that level as a single layer, I often think, if you like, of graphite as a pack of cards. And if you could just peel one of those cards off, thatís effectively what youíre doing when you produce a single layer of graphene.

Chris - And when one stretches or applies a force to graphene. We said itís about 300 times stronger than some forms of steel. Is that because youíre literally pulling along the sheet? So, your trying to pull carbon atoms apart, and so youíre spreading, effectively the force of trying to pull on it, across the entire sheet amongst all the atoms - and thatís why itís so powerful?

James - So, 2004, when the first isolation happened, the so-called superlatives. Now, all these fantastic properties that have now being discovered since that first isolation Ė like stronger than steel, more conductive than copper, transparent, flexible, stretchable. Effectively youíre stretching that carbon chain, and itís got these properties that give it such a wonderful range of possibility for future applications.

Chris - If one looks at chicken wire, the striking thing is that itís mostly all holes. So, if one looks at graphene, that presumably is also, mostly all holes Ė is that why light goes through it so easily and so well?

James - Itís not fully transparent, It's about 97% transparent as a single layer. Graphite, as you probably know is dark. Itís black. Itís not transparent at all. But one of the properties you can now have is you can now start using those layers in different ways. So, for example, you can make it transparent. You can make it strong. You can make it flexible. You can also make it permeable or impermeable to gases and water which is another reason why thereís a whole range of properties being looked at for graphene.

Chris - Why is it then impermeable to gases? Because youíve got these fairly big holes, if I return to my chicken wire analogy, Iíve got lots of space. Why wouldnít, say, water molecules or small gas molecules or gas atoms fall through the holes?

James - So, the scientists now are doing a whole range of experiments. Having isolated the graphene, we can now effectivelyÖ I'll call it, tune the different layers of graphene. So, through experimentation itís been shown that you can effectively tune the layers to only allow certain size of molecules to pass through or to be repelled, if you like, by the graphene barrier. So, ultimately, for example, water desalinization is an area of huge interest in research, both for research applications but also for commercial applications. Imagine having a membrane made out of graphene that could separate, for example, dirty, salty water and you could produce pure drinking water through that membrane - what a fantastic commercial application, if you could actually achieve that.

Chris - Could you do the same thing with gases? Could we clean up waste gas or scrub out, say, carbon dioxide from a power station flue? Can you filter gasses in this way, in a molecular way with graphene?

James - Iíve mentioned itís tuning properties. So, again, there are different applications for gases, for liquids. A simple experiment weíve done in the University of Manchester is one where weíve separated water from fuel, just to give an example of a liquid. But also, as you say, weíre looking at separating gases. So, cleaning up the air might be a possibility for graphene in the future.

Chris - Is it easy to do that, James? Does it take a lot of tweaking to get the graphene to do that and, therefore, is it scalable? Could we make an industrial filter based on graphene?

James - Lots of the experiments today are still being done in a laboratory. But increasingly now, weíre starting to see applications being developed using graphene as an additive, probably in the first instance. But yes, it is still quite a challenge to scale up and to get the purity, and the volume of the graphene for these commercial applications today. But graphene is still relatively young Ė 2004. For a new material, itís still relatively young. So, weíre starting to see quite rapid advances but, not yet to industrial scale for some of these exciting applications but weíre getting there.

Chris - Graphite is a very good conductor of electricity, isnít it? So, presumably therefore, graphene which makes up the graphite is too. Why is that? And why might that be useful?

James - So, again, these fantastic properties of mixing different layers, different forms of grapheneÖ again, graphene is a very broad term and there are many different ways of producing graphene from different processes Ė either form graphite or from chemical mixing of materials. But by certain ways of producing that, you can also try and enhance the electrical conductivity. So, again, some fantastic opportunities, either as a coating or as an additive into a polymer or into a composite, we can exploit some of those thermal management properties. So, the transfer of heat away from a light bulb, for example, is a good example. Again, a partner weíre working with in Manchester has used a graphene layer within an LED light bulb to dissipate the heat more effectively than a conventional metal filament. So, again, youíre starting to see graphene appear in products for the future.

Chris - If itís made of carbon and therefore likes oily things, does this mean that you could potentially also add it to things like oils and have a better lubricant for your engine that will also take heat away from the components itís trying to lubricate?

James - Sure. Yeah. To date, people are looking at the graphene properties for lubricants. Today, there are companies who are actually adding graphene to lubricants for drilling to take the heat away from the drill head. But again, companies are potentially looking at exploiting those properties in a whole range of different applications, which again, is why itís so exciting from all these different markets and applications for the future.


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