Graphene has been a really hot topic since its discovery in 2004 when atomically thin sheets of carbon were peeled off graphite by University of Manchester scientists Andre Geim and Konstantin Novoselov. Since then, the material has received great publicity, significant funding and more than a little hype in the media. So how do we assess the potential of graphene and its increasing number of compounds and planar relatives?
Lux Research recently published a report entitled “Is Graphene the Next Silicon…Or Just the Next Carbon Nanotube?”. Apart from eliciting a wince reaction from those of us who have worked and are working with carbon nanotubes (CNTs), the title asks a very valid question that begs an answer - how can we do a better job with graphene than we did with CNTs? These are my thoughts after reviewing personal experiences and observations on both CNTs (for obscurant and composite applications at NanoDynamics) and graphene (working with two graphene production companies at TPF Enterprises and recently starting a Department of Energy STTR with Cornell University on higher order microwave absorbers at the NanoMaterials Innovation Center).
CNTs were heavily promoted but fell afoul of many pitfalls including:
- Hype in the popular media – space elevators anyone? – stressed the fantastic theoretical properties of CNTs but measurable materials properties have fallen short of theoretical by a very wide margin.
- Health, safety and environmental concerns – many associated nanotubes with fibers and made the mental link to asbestos. Coupled with this, some early biological and other testing was done on materials that may have been heavily contaminated with transition metal catalysts and may have measured the catalyst metal properties rather than the nanotubes. Standards work as carried out by ANSI, ISO, ASTM, IEC and others is critical in defining how CNTs are characterized.
- The high cost of low-volume production. It doesn’t matter what you make, the more you make of it, the cheaper it gets! (Recommended reading: Nagy B, Farmer JD, Bui QM, Trancik JE. 2013. Statistical basis for predicting technological progress. PLoS ONE 8(2): e52669. http://dx.doi.org/10.1371/journal.pone.0052669). This means that early-adopter applications are in small volume high value applications such as sporting goods, specialist non-volatile memory, specialized automotive and aerospace. Only now are larger-scale applications in composites becoming more mainstream even for carbon fiber.
- Developing the processing technologies takes time. Groundbreaking device fabrication using electrophoresis and other novel techniques at locations like the Center for High-rate Nanomanufacturing take time to develop, scale and gain acceptance. Nanotubes were discovered in Russia in 1952 and have had 60 years to reach this stage of commercialization. Production capacity projected for 2013 is about 5,000 tons with much less than 50% utilization.
- The IP land grab. Google Patent lists 399,000 references to CNTs! The United States Patent and Trademark Office database lists 8949 patents (as of 3/28/2013). Untangling overlapping claims will keep attorneys busy for decades.
- Lack of a “killer app”. Typical of technology push products, there are many potential applications. It is not clear which will become the dominant applications – if indeed there will be a dominant application. For example, after maybe 30 years airbag sensors were the “killer app” for MEMS accelerometers – now that market is dwarfed by the market for accelerometers in smart phones; both markets that didn’t exist when MEMS devices were invented. Predicting the future is tricky!
- Competition from silicon (semiconductors and sensors) as well as carbon fiber (composites) is fierce.
Graphene is following a similar path in some ways:
- Graphene is also heavily hyped and reported, and various agencies world-wide are funding research heavily. The EU’s billion-euro program is looking to make Europe a leader in commercializing graphene. As to developing products that approach the theoretical properties – we’re still working on them.
- The health, safety, and environmental concerns have not raised as many red flags as with CNTs but we still lack strong standards. Nevertheless, concern has been expressed that free nanoplatelets might cause respiratory issues.
- Graphene costs are still about 10 times the cost of CNTs. They have had only 9 years to move down the experience curve. Published capacity is less than one tenth that of CNTs.
- There are several chemical and mechanical pathways to make graphene – it is surprisingly easy to make graphene (for example, check out Graphene from Girl Scout Cookies)…but remarkably difficult to make in a useful form!
- Graphene has less US patents granted (1608) but many are in the pipeline and graphene is catching up! China, the US, and South Korea lead in patent publications. As of 3/18/2013, 1926 U.S. patent applications had been published filed in 2012, vs. 3049 CNT patents (a ratio of 1:1.5 compared with 1:5.6 for granted patents).
- Graphene has some applications in common with CNTs and some differences. Much of the effort is aimed at transparent conductive coatings to replace indium tin oxide but there are also applications in batteries, composites and sensors similar to those for CNTs. The projected “killer app” for graphene is definitely transparent conductive films for displays, but that is not proven yet. Enhancement of conductive inks and composites appear to be shorter-term opportunities.
- Graphene has many competitors, not just from established materials, nanowires and CNTs but also from its planar “cousins” such as boron nitride, molybdenum disulfide, tungsten disulfide and others. Some of these have attractive electrical properties – for example, a practical band gap which makes their electronic properties rather interesting. Un-doped graphene has no band gap.
So how do we stop the 2D market from being flat (in a business context of course!)? One initiative that is being unveiled at the NanoBusiness Commercialization Association meeting in early April is the non-profit Graphene Stakeholders Association that will bring together researchers, industry, government, NGOs and the finance community to encourage the responsible commercialization of graphene and other 2D compounds by learning from past experience, facilitating information exchange and standards development. Device designers and fabricators can mingle with producers and researchers to facilitate the development of the new applications and products graphene needs to grow.
Graphene has great potential - but we really need to learn from its predecessors to ensure its steady progress.