Graphene: Revolutionary Material or a Pipe Dream?
Graphene has been hailed as a wonder material which could potentially revolutionize the technology industry over the remainder of the 21st century due to its unique and valuable properties. So what are the intrinsic characteristics which separate graphene from other materials? What kind of innovations will the material allow? What potential obstacles are there which may prevent the full realisation of graphene’s potential?
Graphene is essentially a single atom thin layer of graphite, a compound which naturally occurs as flakes within metamorphosed, carbon-rich rock. It is a two dimensional sheet of single carbon atoms arranged in a honeycomb structure which is not only remarkably flexible but extraordinarily strong. It is claimed to be harder than diamond and around 300 times harder than structural steel and that it would require the weight of an elephant balanced on a needle-point in order to break through one atom thick layer.
Graphene is also extremely light weight and it has been claimed that a single sheet of the material, large enough to cover an entire football pitch, would weigh less than a single gram. Additionally the material is able to conduct electricity and heat with a high degree of efficiency. The two dimensional arrangement of the carbon atoms allows electrons to pass through a sheet of graphene at 100th of the speed of light.
It is speculated that these unique properties will lead to graphene being utilised in a huge range of disciplines but arguably one of the most immediately appealing applications is within the optical electronics industry. The fact that the material is ultra-thin, near-transparent and highly conductive means that it can be utilised to develop touch-screen displays for devices which are highly flexible and is being touted as a more cost effective alternative to iridium tin oxide, the brittle and expensive material currently used in transparent electronics manufacturing.
A research team employed by the electronic powerhouse Samsung has already created a flexible touch screen by using polymer-supported graphene to make the transparent electrodes. James Tour, a professor of chemistry at Rice University believes “You could theoretically roll up your iPhone and stick it behind your ear like a pencil”.
The unique properties of graphene may also allow the development of digital LCD windows which would be able to alter from an information display to transparent at the flick of a switch. These ‘Smart Windows’ could be constructed using a layer of liquid crystals sandwiched between two flexible electrodes comprised of transparent polymer and graphene. The window would be able to shift between opaque and clear depending on the state of voltage bias applied between the electrodes.
The strength and lightweight nature of graphene also makes a suitable candidate for combining with other compounds to manufacture composite materials tailored to have specific physical characteristics such as those required to increase aircraft fuel efficiency.
Additional applications being proposed for the material include the development of super capacitors, increased storage lithium ion batteries and nano-diodes to promote future high-speed electronic performance, the creation of bioelectric sensory devices to monitor human physiological factors such as DNA sequencing, glucose and haemoglobin, and as a potential replacement for silicon and iridium tin oxide in the manufacture of cheaper and more effective photovoltaic cells.
However, many researchers have called for caution with regards to the seemingly miracle properties of graphene, mainly because many of the claims are based on theoretical potential with few working examples to support them. Dr Yu-ming Lin, at researcher at IBM previously stated “The kind of strengths that people quote may not even apply to microscopic samples, so, while it may be true that on a local level it has this strength much stronger than steel, we have to be careful about these claims”.
Another concern which may prove a stumbling block in realising graphene’s potential is the lack of a band gap, an attribute of solid-state physics which allows nano-electronic devices to be turned off. Artificial band gaps would have to be engineered into graphene in order for it to replace silicon in future electronic devices.
Yet another obstacle to overcome is the difficulty of producing the material in industrially useful quantities. Current production techniques such as mechanical exfoliation and chemical vapour deposition do not generally exceed 0.4 grams per hour, with the latter process also being prone to atomic defects which can negatively affect the materials performance.
However, a research team from Trinity College in Dublin recently made a breakthrough in demonstrating its production using nothing more than a blender, water and dishwashing fluid, a process which they believe can be scaled up in order to yield industrial useful amounts. However the quality of graphene produced using this method is not suitable for all of the potential applications being proposed.
Analysts at Research and Markets have forecast that the market for graphene will grow by 60.4 percent over the period of 2012-2016 but concede that the high cost of production could inhibit this projection. This will likely increase substantially over the foreseeable future as the full potential of graphene is realised.
Hence, the global demand for graphite is also likely to experience significant growth. Fortunately, graphite is the 15th most abundant mineral within the Earth’s crust but the fact that China, a country currently experiencing something of an environmental crisis due to poor industrial regulations, currently produces over 70 percent of the world’s graphite raises concerns. The Chinese government recently closed over 200 flake graphite mines due to deteriorating air, soil, and water quality as a direct result of high levels of graphite dust being released into the atmosphere and this is expected to result in a 30 percent increase in market price.
Furthermore, only 40% of global production actually yields flake graphite, essential for the creation of graphene. Of course, high quality graphite can also be synthesised artificially from petroleum coke, however the highly expensive process is not seen as a viable industrial source of graphite due to the high energy inputs required for the reaction.
The remarkable and unique properties of graphene, at least on a theoretical level, do seem to suggest that it will be a valuable material with a wide range of potential future applications. However, there appear to be many technical, logistical and environmental challenges to overcome before its full potential can be realised and it can be crowned the revolutionary wonder material of the 21st century as is currently being predicted.