Behind the hype: experts explain the science behind graphene, the new supermaterial
A single sheet of graphene could hold an elephant and not break
The story might be familiar by now: The material in our lowly pencils — graphene, a version of carbon — could change the world. There’s graphene-enhanced eyewear and graphene-inspired condoms, but is this all hype? Beyond the buzzwords, what exactly is graphene, and what are its real possibilities?
Graphene-inspired eyewear might not amount to much, but graphene really could hold the key to advanced bullet-proof armor and lighter and safer smartphones, say scientists Joseph Meany and Les Johnson. They’re the authors of Graphene: The Superstrong, Superthin, and Superversatile Material That Will Revolutionize the World, out February 6th from Prometheus Books. The Verge spoke to Meany and Johnson about the science behind this material, what it could do, and what we have yet to figure out. This interview has been lightly edited for clarity.
The Verge: Let’s start from the beginning. How did the two of you meet? And how did you end up writing a book about graphene?
Meany: Les is the co-founder of a science group called the Tennessee Valley Interstellar Workshop, which I joined. Les got to know my work and just asked me off the cuff, as we were walking past each other, how much do you know about graphene? ‘Well, a lot,’ I said, it’s a conducting organic molecule and it’s what I’m getting my doctorate in. And he said, let’s follow up, I want to write a book with you. And then we took it and ran with it.
Johnson: For me, it started with solar sailing. In my professional capacity I work for NASA —and to be clear, I wrote this book on my own time so all this is my own opinion and not that of NASA. So, in my day job, I’m an expert in using solar sailing and I’ve got a mission using a solar sail that’s roughly the size of a school bus. Think of a sailboat, which moves by reflecting wind. On solar sails, instead of wind, you can use sunlight to move out of really big sails, hundreds of square feet if not thousands.
The one we’re using is made of plastic, but I’m always at the future, and the first time I got interested in graphene, I was reading about it and thinking ‘Wow, if only we could make this in large quantities!’ It’s extremely lightweight and extremely strong. Put a reflective coating and it would make a fantastic sail for a future solar mission.
I understand why a lightweight and strong material would be great for a sail, but let’s back up. What exactly is graphene? What’s so special about it? All I know that there’s the mineral graphite, and graphene is just one layer of it.
Meany: Graphene is a sheet of carbon atoms that all lie in a single plane next to one another. It’s repeating hexagons of these ball-like carbon atoms that extend on in atomic scales for great distances.
It’s extremely flexible. If you were to take up a piece of graphene — and to be clear, we haven’t made a sheet of graphene that you could pick up in your hand and wave around — but if you could, it’ll be lighter than a feather. It’s going to be extremely flexible, moving and billowing like very light fabric in the wind. And the way that the carbon atoms bond together to one another makes them extremely strong and makes it extremely conductive for electricity.
Les Johnson
Johnson: To put this in perspective, graphene by weight is hundreds of times stronger than steel. I’ve seen one calculation that one sheet of graphene, which is one atom-layer thick, you could put an elephant on it and it wouldn’t break, so that’s amazing.
And the challenge is getting it in large quantities. Right now we’re making sheets that are millimeters as opposed to meters, but consider that it wasn’t really isolated and studied until 2004.
So how do you produce graphene? What are the innovations?
Meany: One of the more common ones and more cheap methods for producing graphene is actually literally just mining graphite out of the ground and chemically separating the graphene plates. This separation process is called exfoliation and it’s actually quite analogous to skin exfoliators. By treating graphite with a specific process, these plates of graphene just come off the surface into a powdery suspension that can be isolated and turned into whatever further product that the manufacturer is looking to do.
Another production method is called chemical vapor deposition, or CVD, and that’s where scientists take a gas of hydrocarbons along with a metal catalyst and are able to remove the hydrogen atoms from the hydrocarbon, then keep only the carbon atoms and then hopefully these carbon atoms kind of arrange themselves side by side into this graphene lattice form.
And then the third major production type is called epitaxial graphene. Basically, it’s carbon that’s been embedded within silicon carbide. By heating that up to very high temperatures you sublime off the silicon, leaving behind a large excess of these carbon atoms that are really just dying to bond to anything around them, and so they’ll latch onto something together and create these graphene sheets.
Johnson: What you see from all of these is that there’s really lacking a good process like we have for sheets of plastic, which is a spray that dries and self-bonds. You don’t really have anything analogous for the graphene. Part of that is just the challenge of, how do you get something that is composed of only one element to basically bond with itself outside of some kind of extreme condition? I don’t know the answer to that question, and whoever figures it out is going to make a lot of money.
Do we have graphene in materials now?
Meany: Graphene has already found its way into a number of different consumer products. It’s already out on the market. It’s very tiny amounts of graphene being mixed into things like rubbers and plastics and cement and paint and inks.
It’s being used to enhance and to change the properties of the other materials. The production problem lies in making very large sheets of graphene, say those that you would be able to pick up and look at with our own eyes.
Why mix in tiny amounts?
Johnson: Graphene mixed in with something can increase its structural strength even without having a complete sheet. It can make it more robust and less resistant to wear. It can be used as a lubricant, it can store electrical power.
Of course, you’ll also find things now that are products that claim to have graphene in them, I’m not sure what the improvement really is in a quantifiable way. I think a lot of people are jumping onto it as a catchword and making people think they have a “gee-wiz” material, like this glasses company I saw saying they have graphene in the glasses.
What are some other examples of the use of graphene?
Meany: There are a couple of bike companies that have put out bicycle frames involving graphene and carbon fibers and these bikes are supposed to be extremely light, extremely strong, and for athletes racing at the Olympic level.
Some Irish scientists ended up taking graphene powder and mixing it within silly putty and they found that they could detect very tiny vibrations within the electrical current change through this silly putty-like wire so they think you could make very sensitive vibrational detectors out of very cheap and robust materials.
And, recently, a couple of researchers found out that if you take one layer of graphene and two layers and stack them on top of one another, when a large force contacts the graphene on one side, and pushes the two together, that compacting force actually creates a diamond-like bond between the graphene layers, increasing its strength and potentially leading to next-generation bullet-proof armors.
What about in the future?
Johnson: One of the biggest challenges we face today is how to store energy efficiently, electrical energy efficiently. Now, graphene is a very good conductor. It is probably the most efficient conductor we have that’s not a superconductor. It’s better than any metal, better than silver, certainly better than copper.
And graphene is so strong and such a good conductor that you could pack a lot of these plates in a very small volume and store a tremendous amount of energy. I envision one of the first breakthrough applications for graphene are in batteries, giving longer life and much lighter weight and probably making them safer. So your phone, your electric car, all of those will benefit. And, because graphene is very thin, very lightweight, electrically conductive, and essentially transparent, it sounds like the perfect cell phone screen.
There’s of course been a lot of buzz around graphene. How likely is all of this to happen?
Johnson: This is all hypothetical, of course, and we don’t want to come across as mindless cheerleaders. Every 20 years there’s some breakthrough and some of these things go absolutely nowhere. But others have taken off and have changed lives and I think graphene is at that precipice. If we can figure out how to use it, it will be just a dramatic impact on our lives, but there’s always a chance that as we learn more about it, it can’t do all the things people think it can do.
Meany: My opinion is that once we can control the graphene production process so that we can make a centimeter square flake of graphene, it might as well be a hundred meters or a thousand meters squared. Once we crack production process we can control the size, there’s going to be no real stopping all of the really out-there application that we can think of for graphene to come along.
And just about all of the economic superpowers across the globe have some sort of focus on graphene. I mean, China, Britain, Russia, India, US, Ireland, and Germany all have some sort of focus on the national level that are supporting university and entrepreneurial efforts to get graphene off the ground because whoever cracks that code first is really going to have a major economic leg up across the global market for graphene itself.
What are some other things we should be taking into consideration when it comes to the potential uses of graphene?
Johnson: This whole notion of the potential of new materials that are 2D like graphene are spurring scientists to look at other 2D materials. We don’t know where these technologies will lead and I hope we do it with forethought in terms of what it means for the environment, how it’s manufactured, human health. There’s a lot of unknowns here. I hope we do it with a bit more more forethought than those who invited Bakelite, which we now call plastic, did.
Meany: Right, we don’t have a lot of clear environmental or health data on the effect of graphene sheets.
Johnson: Yes, and there are people doing very strange experiments. Someone fed water with graphene flakes in it to spiders and then looked at the spider silk that they spun. The spiders spun stronger spider-silk than normal, but a lot died, so you know, you have something that looks really neat but you have to look at the other side, and what happened to the ones that didn’t make it. So people are looking at different things and some of them are straightforward and good science, and others are things we’re still finding out #steemstem
Source:
https://www.theverge.com/2018/1/24/16927224/graphene-materials-les-johnson-joseph-meany-book