Graphene has been referred to as a “miracle material” by CNN, a “super material” by The Guardian, and Physics World has asked “is there anything graphene can’t do?” The material, a single sheet of carbon one atom thick, has emerged as the most studied material of the 21st century with the results of hundreds of studies being published each week. In fact, for the past few years about 1% of all academic papers published in all fields had to do with graphene. These studies have shown graphene to be one of the strongest materials ever measured (strength ~130 GPa, modulus ~1 TPa), with a high thermal conductivity (~5 kW·m-1·K-1) and surface area (~2,630 m2/g), and an unparalleled ability to transport charges (mobility > 200,000 cm2·V−1·s−1 reported). As addressed in Nanotech’s June 2012 issue, graphene could impact a range of markets and industries including aerospace, automotive, coatings, communications composites, electronics, energy, and sensors. To tap the potential of this material, the European Union is funding a 10 year, €1 billion “Graphene Flagship” coordinated program and South Korea is spending over $350M on commercialization activities. Companies have filed thousands of patents worldwide on technologies using the material. Yet for all this academic interest, funding, and intellectual property, only a few companies, such as Vorbeck Materials, have brought graphene-containing products to the marketplace.
Up-scaling
One of the main impediments to widespread use has been the lack of abundant quality material. Using mechanical cleavage such as was performed with the Nobel Prize winning work by Geim and Novoselov in 2004, uses an adhesive such as scotch tape to remove sheets from large graphite crystals. In this way, high quality graphene can be produced but only in batches of nanograms at a time. Chemical vapor deposition has surged in interest with large area films being produced in laboratories. The goal is to move this to a continuous process; however, this energy and cost intensive process, often involving vacuum, high temperatures, and metal etching makes this a nontrivial task. High grade, nanometer thick films produced via these means would be useful in transparent displays and as a baseboard for beyond-silicon electronics. Nevertheless, at production levels of ~0.8 mg/m2, only small amounts of material can be processed. For bulk applications such as composites or inks, an industrial production technique that can fabricate tons to hundreds of tons of material per year is required. One such route – patented by Princeton professors Ilhan Aksay and Robert Prud’homme in 2005 and licensed by Vorbeck Materials – uses graphite as a starting material (see schematic below). This process uses chemical methods and thermal exfoliation to yield primarily single sheets of graphene. The graphene (trade name of Vor-x®) can contain various functional groups and defect sites and these sites can be tuned for specific applications, whether they be to modify the surface’s affinity for solvents aiding dispersion, as reactive centers in sensors, or for interacting with the matrix to improve load transfer in composite applications. This fabrication process and resulting material has been EPA approved, and Vorbeck is producing tons of Vor-x graphene a year at its Jessup, Maryland facility. Well publicized, “high-tech” applications of graphene, such as replacing silicon in integrated circuits, or creating better solar cells and batteries, are in development, including at Vorbeck Materials; however, a more immediate impact will be in printed electronics and high performance rubbers.
Conductive inks
Vor-ink™, a graphene-based conductive ink whose first iteration became commercially available in 2009, looks to not only displace silver and carbon inks in the $3 billion conductive ink market, but create new markets, such as those in smart packaging and wearable electronics. Formulations with resistivity values down to 1 ohm/sq/mil – orders of magnitude lower than traditional carbon inks – have been developed and are commercially available. Although not as conductive as silver inks, low temperature curing, environmental stability (it is not a metal, so it does not corrode like one), flexibility, and a much lower price tag grant major incentives to this product. Currently Vorbeck Materials has capacity to produce ~50 tons of ink per year with expansion planned. Through a partnership with MeadWestvaco inks have been used in antitheft packaging, and a large rollout at major retailers is currently underway. Vorbeck Materials is also working with major apparel manufacturers to bring smart clothing, utilizing a line of graphene-enabled wearable electronics, to mass market in 2014. Electromagnetic interference (EMI) shielding represents another major opportunity for graphene containing conductive inks.
Image 1: Vor-x® graphene powder.
High performance rubbers
A second area in which graphene products are on the market is with high performance rubbers. As oil and gas companies delve into more perilous and harsh conditions, the materials that ensure safe working conditions need to be improved. In January 2014, graphene enhanced rubbers will be available from McMasterCarr with improved mechanical properties and thermal resistance. Furthermore, graphene-enhanced rubbers for lower rolling resistance tires are under development which could improve efficiency an estimated 3-5%, tremendously reducing gas consumption. By comparison, gas displaced by electric vehicles is significantly lower as they currently represent less than 0.1% of the market.
Image 2: Example Vorbeck graphene products on the market.
Electric Vehicles
Electric vehicles, and enabling battery technology will become a larger and larger market – with estimates of CAGR of over 20%. Graphene may very well play a part in improved technologies, as Vorbeck Materials, XG Sciences, Angston Materials, and Grafoid all have plays in lithium battery technologies.
In this field, Vorbeck Materials is focusing on next generation lithium sulfur technology, spurred by a 2012 Department of Energy ARPA-E award. This technology could produce batteries with 10 times the energy density of current lithium-ion technology, paving the way to a widespread adoption of electric vehicles and machinery.
Image 3: Vorbeck Materials Vor-inkTM conductive electronics printed through flexographic techniques.
Image 4: Vorbeck Materials Vor-inkTM conductive electronics printed through flexographic techniques.
Other markets
Other major markets which are promising for graphene technology are:
• Corrosion – In the United States alone, corrosion costs about $300B each year, with major losses in public works, utilities, and the automotive sectors.
• Transparent conductors – The rise of touchscreens and photovoltaics is increasing the need for non-indium based transparent conductors. Furthermore, flexible touch screens such as those touted by Samsung and Nokia, would require a non-brittle material.
• High strength composites – Carbon fibers took about 30 years to enter the market and are still deemed too expensive to fully utilize. Carbon nanotubes have been trying to gain traction for over a decade, but it looks as though graphene with its cheaper fabrication may leap frog its rolled-up counterpart.
Competing materials
Due to graphene’s comparable or better properties and lower production cost, carbon nanotubes will be replaced in applications which do not significantly benefit from nanotubes’ 1-D nature. It remains to be seen how graphene powders will compete with incumbent carbon blacks in rubbers and other composites, and where the markets place the tradeoffs between price and performance. Yet there can be no question that graphene materials will creep into the carbon black markets, especially for higher performance materials. Graphene’s incorporation into the marketplace is just beginning, and all signs point to strong growth ahead.
AUTHOR: Joe Roy-Mayhew, Vorbeck Materials
E: Joe.Roy-Mayhew@vorbeck.com, T: +1301-497-9000
All graphene images courtesy of Vorbeck Materials.
