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What is Graphene and what can it do?

by YPU Admin on January 31, 2017, Comments. Tags: graphene, PhD, Research, STEM, and UoM

Introduction

Hi, my name is Rory Brown and I’m in the second year of a PhD in theoretical physics. Specifically, I’m a part of the Graphene NOWNANO CDT at the University of Manchester, a programme that takes in students from all STEM backgrounds and trains them to do research in different areas of nanotechnology, mostly related to graphene and other similar materials – I use computer modelling to study how graphene behaves when we combine it with other materials to make electronic devices, and try predict if anything unusual will happen. I’ll tell you a little bit about what graphene is and hopefully explain why it’s so exciting, then what a PhD is like and how you can get there.


In Depth

Graphene was discovered here in Manchester in 2004, through an experiment so simple you can do it in 5 minutes at home. We start with graphite, the same material that we use in pencils. If you’ve ever held a piece of graphite, you might notice that it feels slippery and waxy – this is because graphite is made of layers of carbon atoms, organised in hexagons and stacked together like a deck of cards. Each layer is strongly held together but can freely slide over one another, and when you write with a pencil you break these layers apart, leaving some behind on the page. Graphene is a single one of these layers, and for a long time people argued that a single layer couldn’t actually be separated from the others, thinking it would be too unstable. It’s actually surprisingly easy to make – reaching in with a piece of scotch tape, the Manchester team was able to pull these layers apart over and over, until they finally had flakes of single layers of graphene, a material 10,000 times thinner than a human hair. Given that it’s only one atom thick we say it’s a ‘2D’ material, and since its discovery we’ve found a whole family of materials that can be made 2D.


Picture a: a sheet of graphene. Picture b: how graphene stacks are weakly bonded to make graphite.

So now that we’ve made it, what can graphene do? As well as being incredibly thin it has some remarkable properties, being incredibly flexible as well as the world’s strongest material: if you had a sheet big enough it would take the weight of an elephant balanced on a pencil to break through it! Industries are already looking into using graphene to make stronger, lighter materials for e.g. cars and aerospace travel. I’m interested in its electronic properties: electricity in graphene travels without any resistance, only 300 times slower than the speed of light, which gives it a lot of potential for energy-efficient electric devices.

One of the ways to make these devices is to combine graphene and other 2D materials, making thin sandwiches of different materials. What we’re left with is a stack only a few atoms thick, and the atoms in each layer can have different properties – one can be an LED, or a sensor. This is where I come in, making computer programmes to try and describe what happens in these layered materials. Working as part of this big group effort to improve our understanding of this new technology is very exciting and rewarding.

How I got here


My path to doing my PhD was fairly straightforward – I studied an MPhys in Physics here in Manchester, and my interest in graphene led to me staying. This isn’t always the case, and the NOWNANO CDT is a great example of how this can work: the people I work with come from a variety of backgrounds across all of STEM, some having spent time in industry beforehand. I’d love to continue with research, but there’s a lot of potential in PhD studies beyond that: you can go into scientific research or work in industry, or if that’s not your thing the skills that you learn (independent research, problem-solving, numeracy, presenting…) can lead to just about any job you can name. It’s a fascinating position to be in that’s full of opportunities all around the world.

Going Further

If you’re interested in some of the cutting-edge graphene research facilities that we have in Manchester, I recommend looking at the National Graphene Institute and NOWNANO websites:

http://www.graphene.manchester.ac.uk/

http://www.graphene-nownano.manchester.ac.uk/

The Museum of Science and Industry in Manchester also has an exhibit on graphene and other ‘Wonder Materials’ running until June 2017 that’s worth a visit:

http://msimanchester.org.uk/whats-on/exhibition/wonder-materials

Graphene also tends to pop into the news every now and then because of the promising factors just mentioned, so keep an eye on the science sections!


The National Graphene Institute.

 

An Insight Into Nature's Strongest Force

Introduction:

My name is Lloyd and I am in the third year of my PhD studying Theoretical Nuclear Physics. I am attempting to provide a better theory to describe the phenomenon of neutral pion (a relatively light, short-lived particle that is found in nuclear and particle reactions) production from a photon (light) incident on a proton (a nuclear particle that is found in the nucleus of every atom).  Before starting my research I studied theoretical physics at the University of Manchester.


Strong Nuclear forces remain to be one of the least understood processes in nature. Yet it is the source of immense energy that can power our cities, from harnessing the emitted radiation in power-plants; or level countries by concentrating radioactive materials in a bomb. The manner in which the fundamental matter particles (or quarks) exchange the strong force carrying particle (or the gluon boson) is far more complex than any of the other forces (weak nuclear, electromagnetic or gravity). Unlike the other forces, gluons themselves can carry a strong nuclear charge, known as colour charge; this allows them to interact with themselves in-between quark interactions, allowing for infinite scenarios to describe the simplest of processes. 

In Depth:

The study of the strong nuclear force is known as quantum chromodynamics (QCD), this theory helped scientists understand important properties of particle physics, mainly why we only see composite quark states in nature. In other words why you will never find a sole quark by itself, instead you will see it in bound states (hadrons) which form protons and neutrons (baryons) and lighter states such as pions (mesons). But trying to make any practical calculations with QCD is very difficult, so difficult in fact that if anyone were to solve the QCD equation into a usable form then they would win 1 million dollars from the Clay Mathematics Institute!

I do away with these complexities of QCD by only working in energy regimes where the protons and other hadrons won't break down into their constituent quarks. So we can describe proton or neutron scattering through pion exchange instead of using gluons. Furthermore, I take advantage of some symmetries present in QCD, related to the quark masses, to simplify aspects of the calculations. This is a very vague picture of the theory I work in called Chiral Perturbation Theory (ChPT).


My work has been motivated by a recent experiment in Germany at the Mainz Microtron by the A2 and CB-TAPS collaborations where they have obtained the most accurate data to date on this interaction. I am in the process of taking theories that have already been made to describe parts of this process and sticking them together to get a more complete picture of the reaction. The most important part I have included is an intermediate resonance state prior to pion emission.

This research isn't going to be part of the new fastest computer in 20 years time, nor is it going to cure diseases. But it will give us an insight in to what happens in nature at the sub-atomic level. Then maybe who knows what this might lead to in the future, 100 years from now it is impossible to predict how important this process will be in understanding nuclear fusion both in power plants or in stars. When Paul Dirac, one of the pioneers of quantum mechanics, predicted the existence of massless Dirac fermions in the 1920s he had no idea that a century later people would be trying to use these states within graphene to dramatically improve technology.

Going Further:

To follow exactly what it is I do I am afraid you will need a degree in theoretical physics, which you can start looking into at the University of Manchester. (http://www.physics.manchester.ac.uk/study/undergraduate/undergraduate-courses/physics-with-theoretical-physics-mphys/)

The European Centre for Nuclear Research (CERN) have lots of information available on particle and nuclear physics (http://home.web.cern.ch/students-educators)

The Jefferson Lab in the USA also has useful information for students and teachers (https://www.jlab.org/education-students)

MAMI, the experimental group that analyse this interaction (http://www.kph.uni-mainz.de/eng/108.php)