Special Report: Endless possibilities with graphene

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Fig. 1 TEM image of CealTech’s 3D graphene

CealTech AS, Norway, enables the large-scale production of high quality graphene, heralding revolutionary products across various industries.

Graphene is a two-dimensional (i.e. one atom thick, which equates to 0.345nm) planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb-shaped crystal lattice. With at least one dimension less than 100nm, graphene is a nanomaterial, at least by definition. Graphene has extraordinary material properties, including an ultimate tensile strength of 130 gigapascals, an electron mobility of 15,000cm2 .V-1.s-1, a thermal conductivity between 2,000 and 4,000Wm-1K-1, and an optical transparency of 97.7% (Fullerex Report, 2017).

These unique properties explain the proliferation of production processes that have been developed in an attempt to create this paradigmatic material, resulting in the emergence of a broad spectrum of graphene-based materials. These range from a single layer of carbon atoms to those comprising tens or even hundreds of layers in a stack, essentially nano-graphite.

While the strict definition of graphene is that of a monolayer material, generally, the thicker the graphene material the less exceptional its properties become. Accordingly, as one moves from multi-layer to monolayer across the broad range of graphene materials, the overall mechanical and conductive properties of the material increase, as well as surface area per unit weight, overall cost, and time to produce. In addition to the number of layers, there are also significant property changes that arise from any intrinsic defects in the crystalline structure (dislocations, tears and grain boundaries), and/or extrinsic defects (chemical impurities such as foreign atoms), where such defects limit the benefits of using graphene.

The ‘Holy Grail’, therefore, is the ability to produce industrial volumes of pristine single-layered (or very few-layered) sheets of graphene for a reasonably low cost.

Enter CealTech AS

Since its inception in 2012, CealTech has sought to be an industry leader of high quality, high volume graphene, thereby unlocking its full potential. To this end, CealTech has entered a global strategic collaboration agreement with Caltech (California Institute of Technology) focused on the research and development of graphene and utilising Caltech’s patented graphene production technique (issued US patent 9,150,418). The collaboration and licensing agreement was made effective as of 15 June 2016, granting CealTech exclusive rights for use of the patented technique in its own graphene production unit, FORZA™ (patent pending), which has the potential to produce graphene on a large scale and at a competitive price, with effective yields and a purity sufficient so as not to impair graphene’s desired properties.

The backbone of CealTech’s graphene production method is the Plasma Enhanced Chemical Vapor Deposition (PE-CVD) technique. The purity, electronic properties and mechanical strength of the PE-CVD graphene are comparable to those of pristine graphene. In addition, CealTech’s unique method enables a short production time, reduced process temperatures, single-step processing (e.g. continuous production), superior control over the number of produced layers, and the ability to directly functionalise the graphene for the intended application without any chemical modification. The Transmission Electron Microscope (TEM – Fig. 1) highlights the unique structure of CealTech’s 3D graphene, which offers better bonding with the surrounding matrix and improves the interfacial load transfer.

In addition to aspiring to high quality graphene at the industrial scale, CealTech is committed to developing and commercialising graphene-enabled products and solutions, such as batteries, composites and coatings with enhanced mechanical and electrical performance, biomedical sensors, transistors, super capacitors, and printed electronics. In that respect, CealTech’s business portfolio encompasses everything from raw (i.e. the graphene itself) and manufactured materials (i.e. graphene doped with oxygen, nitrogen organic and inorganic molecules, etc.) to component parts and finished products such as battery electrodes, paints and coatings, and conductive inks, etc.

The impact of graphene

More specifically, CealTech sees the use of graphene (for example, as a conductive nano-filler in the preparation of inorganic/polymer nanocomposites) as a solution that can assist the wind energy industry in overcoming problems connected to wind turbine structures, such as lightning strike protection. In addition, graphene, owing to its barrier properties, can enhance the anti-corrosion properties of the resin since it absorbs most of the light and provides hydrophobicity for repelling water. It is noteworthy to mention that all these improvements can be realised even at very low filler loadings in the polymer matrix; accordingly, a very small amount of graphene can significantly improve the physical properties of neat polymers.

Furthermore, CealTech expects the impact of graphene-based composites and coatings to reverberate throughout countless industries, enhancing performance and increasing application possibilities. For example, the use of graphene in paints and coatings can address market needs such as anti-fouling coatings for boats and fish farms, solar paints to absorb and transmit solar energy, paints that provide insulation for houses, and anti-rust coatings, amongst other things.

Other areas of application

Battery technology is yet another area of application, where graphene is set to iron out the current ‘bugs’ of, for example, Li-ion batteries by providing a safer and more cost-effective battery with outstanding specific energy, a quicker charge rate, and superior cyclic stability. Such new battery technology will accelerate the electrification of the transportation industry whilst meeting the increasing market demand for energy storage (i.e. smart-grid structure) and power consumption.

Moreover, graphene is the best candidate to achieve both targeted and controlled drugs deliveries alike, pending the proof of its biocompatibility. Among the medical applications that can leverage the unique properties of graphene are cancer and gene therapies, where graphene-based nanomaterials functionalised with known biopolymers can be successfully loaded with several drugs to achieve a precise targeted treatment. Poorly soluble substances can then be conjugated with graphene and its derivatives to increase their solubility and stability without losing their efficiency. Other medical applications which graphene can benefit include, to name but a few, diagnostics and biosensors, tissue engineering, and biomarkers.

Graphene also has a wide number of potential applications in the defence industry, including in advanced camouflage systems and lighter, stronger ballistics protection. By doping graphene, it is possible to develop graphene-enhanced perovskite and DS solar cells. Furthermore, a graphene-modified drilling fluid will only revolutionise the drilling industry, resulting in safe, more cost-effective and more environmentally friendly drilling operations, in addition to reduced flow friction and lower power requirements to drive the pumps. One can also cite all the benefits graphene and graphene-enabled products can bring to the aerospace industry in terms of improved mechanical properties, reduced weight, extended lifetime, better insulation and, most importantly, increased safety.

Challenges ahead

Until the manufacturing process is mature enough for it to be used as a key material in products, it is expected that graphene will continue to be used as a supplementary material in the short term. The barriers to widespread industry uptake mirror those of carbon nanotubes: functionalisation and dispersion; mass manufacturing at an acceptable cost; and alleviating health and safety concerns.

While the industrial adoption of graphene depends primarily on addressing the challenges above, a downstream-focused approach is essential to foster concrete commercial benefits across key industries. Accordingly, it is paramount with such programmes as the Graphene Flagship to hasten the pace at which we start to see more practical applications of graphene and new technologies, build awareness about the vast potential of graphene, and facilitate partnerships and collaborations across the various stakeholders in the ecosystem (e.g. between industry and academia, and/or between upstream and downstream producers).

Furthermore, it is important to address the lack of transparency in the actual quality and characteristics of material that is being produced and sold as ‘graphene’. This stems from the lack of universal standards for graphene materials, and requires the immediate establishment of a system to certify the quality of commercially available graphene. Without an agreed global standard in place, we are not only delaying the adoption of graphene, but facing the risk of an irreversible mistrust and disinterest in the real potential of this ‘wonder material’.