Graphene: Where is it now?
by Dave Ashworth, PhD student. Originally published in issue seven of Resonance.
What do a pair of headphones, a tennis racket and a supercar share in common? The answer most would give is a confused "not much?". However, with the roll-out of graphene into useable devices and technology, you can now get your hands on graphene-containing varieties of all three.
Discovered 14 years ago, after decades of being nothing more than theory, graphene has had a relatively short period of time to establish itself as a viable material that can be utilised across global industry. We’re routinely told of its incredible properties – ultra-light, atomically thin, flexible, transparent, more conductive than copper and 200x stronger than steel – scientists have long since run out of superlatives, but has graphene actually lived up to the hype?
What is graphene?
Graphene is a carbon allotrope, much like diamond (see our factfile for others), with atoms arranged in a hexagonal honeycomb lattice, forming planar sheets just a single atom thick. Layers of this stacked on top of each other form a much more recognisable form of carbon – graphite – otherwise known as pencil lead.
Properties of graphene
Carbon is non-metallic, so you’d be forgiven for expecting graphene to be the same. In fact, it “behaves” generally much more like a metal, which had lead commentators to describe it as a semimetal or semiconductor. Due to its plethora of extraordinary properties, it is apt to describe graphene as a unique material, at least for now.
Strength and elasticity: Graphene can be stretched up to 25% of its original length without breaking, and will return to its original length (think rubberband). The flat planes of atoms can flex relatively easily without breaking. In fact, graphene is believed to be the strongest discovered material.
200x stronger than steel. This property makes graphene particular useful in composites with plastics to form stronger, tougher and lighter materials for ships, planes and cars, as well as flexible screens.
Weight: Being atomically thin, graphene is incredibly light relative to the surface area it presents. You could cover an entire football field with less than a gram! This lightweight nature is particularly useful in materials design.
Heat and electrical conductivity: Graphene is a far better heat conductor than typical examples, such as silver or copper. The flat hexagonal lattice offers little resistance to electrons. Thus, electrons in graphene have a longer mean free path than in any other material. This allows graphene to conduct electricity superbly, as electrons move through the material at speeds close to the speed of light. This grants huge potential in device manufacture, including batteries, touchscreens, computer processors, transistors, and telecomms.
Optical: With very few atoms to penetrate, graphene is almost completely transparent. It transmits about 98% of white light (compared to approx. 80% for a pane of window glass), yet another reason for graphene to be incorporated into touchscreens!
Impermeability: The structure of graphene means that it can act as an ultra-fine atomic net, potentially trapping gases like hydrogen or carbon dioxide for storage.
Barriers to implementation
Graphene is an awesome material. Combinations of its properties mean it has genuine potential to be a useful material in many diverse applications, as well as representing a major step forward within materials science research. So, why is it not in everything, everywhere?
Synthesis: At the moment, synthetic methods for creating graphene can either create relatively large amounts in low quality (i.e. large defects, multilayered, small lateral size) through bulk delamination from graphite; or small amounts in high quality, through chemical vapour deposition (which is not industrially applicable).
Cost: High quality graphene is incredibly expensive. Low quality graphene can be supplied in large enough quantities for materials research to be ongoing, and companies have made many products incorporating graphene within composite materials. However, high quality graphene is required for electronics, and although demonstrations of potential devices have been made, at the moment the use of graphene is too expensive.
Although an incredible material in its own right, graphene’s most promising uses, at least in the short term, come from using it within composite materials. Much of the research into graphene is still "blue skies", and it could be a number of decades before it becomes cost-effective and practical to include graphene in our everyday life – but don’t write it off yet. Its discovery was only just over 10 years ago, and it’s already possible to buy consumer products incorporating
graphene - shown below! So, although this seems slow in our expectations, is it really taking as long as some think?