The secret to the material’s extraordinary strength lies in the robustness of the covalent carbon-carbon bond and the fact that the one atom thick graphene monolayers can be produced defect-free.
Essentially all materials contain defects, such as microscopic cracks or scratches, which are “weaker” than surrounding material. As a result, the breaking stress of a macroscopic material depends mainly upon the number and sizes of defects it contains, rather than its intrinsic strength.
The graphene monolayers used in the experiments are defect-free because they are so small, something that precludes the existence of flaws: This condition cannot be satisfied in macroscopic materials. Given the known robustness of the covalent carbon-carbon bond (that also gives carbon fibres used in high-performance composites their remarkable stiffness and strength), it is not unreasonable to claim that pristine graphene is the strongest material in the world,” said Kysar.
In the case of graphene, Columbia University’s James Hone, Jeffrey Kysar, Changgu Lee and Xiaoding Wei measured the intrinsic strength of the material, that is the maximum stress that a pristine (or defect-free) material can withstand just before all the atoms in a given cross-section are pulled apart at the same time, at 42 Nm–1.
To put things in perspective: if a sheet of cling film (which typically has a thickness of around 100 µm) were to have the same strength as pristine graphene, it would require a force of over 20,000 N to puncture it with a pencil: The force exerted by a large 2000 kg car!”
Furthermore, according to Hone the intrinsic strength of graphene can be considered as an ‘upper limit’ for the strength of materials, rather like diamonds are for hardness. This could see them used as a theoretical reference for engineers who design materials.
How can graphene be applied to common automotive products?
The answer is it can’t. Yet. However, there is a lot of work going on to find ways of getting it out of the lab and in to products and hardware. A number of companies, particularly in the UK and US, are investing heavily in trying to produce Graphene in volume.
To date Graphene has been used to coat metal and help corrosion. Researchers from Monash University and Rice University in the US have produced a graphene-based coating so thin that it’s invisible to the human eye but it has been shown to make copper nearly 100 times more resistant to corrosion, creating potential for metal protection even in harsh environments.
This opens up uses for a range of applications, from corrosion-susceptible body parts to electronics, offering significant cost savings for many industries.
While the process is still in the laboratory-testing stage, the team are now not only looking at different metals, but also investigating ways of applying the coating at lower temperatures, which would simplify production and enhance market potential.
Yet, other researchers have been able to use a graphene sheet covered by cobalt and cobalt-oxide to offer a cheaper and more durable alternative to platinum, the material commonly used as a catalyst in a fuel cell.
Spanish company Spania GTA says it’s sourced the lightweight material from Graphenano, the top Spanish company in graphene production, using it on components such as the chassis, body and even the interior and engine compartment.
Graphene in Electronics.
Nevertheless, in the short-term electronics will probably be the field where grapheme will make the biggest inroads.
Scientists in the US have already built the first ever solar cell made entirely of carbon, which offers a promising alternative to the expensive materials currently used.
In recent research a team at Stanford university has produced a thin film prototype that replaces the silver and indium tin oxide used in conventional electrodes with graphene.
Interestingly, graphene-based supercapacitors have already proven the equal of conventional supercapacitors; in the laboratory. But now researchers at Melbourne’s Monash University claim to have developed a new scalable and cost-effective technique to engineer graphene-based supercapacitors that brings them a step closer to commercial development.
With their almost indefinite lifespan and ability to recharge in seconds, supercapacitors have tremendous energy-storage potential for everything from portable electronics, to electric vehicles and even large-scale renewable energy plants. But the drawback of existing supercapacitors has been their low energy density of around 5 to 8 Wh/liter, which means they either have to be exceedingly large or recharged frequently.
Professor Dan Li and his team at Monash University’s Department of Materials Engineering has created a graphene-based supercapacitor with an energy density of 60 Wh/liter, which is around 12 times higher than that of commercially available supercapacitors and in the same league as lead-acid batteries. The device also lasts as long as a conventional battery.
To maximize the energy density, the team created a compact electrode from an adaptive graphene gel film they had previously developed. To control the spacing between graphene sheets on the sub-nanometer scale, the team used liquid electrolytes, which are generally used as the conductor in conventional supercapacitors.
Unlike conventional supercapacitors that are generally made of highly porous carbon with unnecessarily large pores and rely on a liquid electrolyte to transport the electrical charge, the liquid electrolyte in Li’s team’s supercapacitor plays a dual role of conducting electricity and also maintaining the minute space between the graphene sheets. This maximizes the density without compromising the supercapcitor’s porosity, they claim.
To create their compact electrode, the researchers used a technique similar to one used in traditional paper making, which they say makes the process cost-effective and easily scalable for industrial applications.
Moving graphene into the mainstream.
According to Professor Li the product is one step away from moving from the lab to commercialization.
Whilst graphene is set to enable faster, stronger and foldable electronic devices, researchers have now found that the single layer lattice of carbon atoms can help keep electronic components up to 25 percent cooler, giving it the potential to significantly extend the working life of computers and other electronic devices.
An international team of researchers led by Professor Johan Liu at Chalmers University of Technology in Sweden found that a layer of graphene is able to significantly reduce the temperature in the tiny areas where the electronics work most intensively and therefore generate the most heat.
Removing heat from these hotspots, which are found in all electronics and are on a micro or nano scale, is important in improving the working life of electronic devices.
A general rule of thumb is that a 10° C increase in working temperature equates to a halving of the working life of an electronics system. Dissipating this heat also takes energy, as evidenced by a 2007 report from the EPA estimating that around 50 percent of energy consumed by data centers in the US in 2006 went to cooling.
According to Professor Liu the normal working temperature of 55 to 115° C in the hotspots cooled with graphene layers has been reduced by up to 13° C.
Whilst grapheme is obviously the super-material of the future, the trick will be to take this out of the small scale, expensive laboratory environment into the manufacturing halls of the motor industry.