Graphene – the next step

Materials World magazine
,
3 Oct 2015

Dr Martin Kemp argues for a way to push through the hype surrounding graphene and reach its full potential. 

Martin Kemp is Chairman of the IOM3 Nano Committee and Founder of Xcience Ltd, a consultancy specialising in nanomaterials development and application. An experienced materials scientist, he was previously Business Development Director of Haydale Ltd, a graphene processing company, and his current focus is the industrial exploitation of graphene.

Considering the high level of global investment in nanomaterials research over the past 15 years, one obvious question rarely asked is, ‘Why do we hear so few nanomaterials success stories?’ This area of materials science has caught the attention of the public in recent years and, in many industries, nanomaterials are now considered a standard material. Your car exhaust catalytic converter probably contains a very advanced material comprising platinum nanoparticles in a metal matrix. Even humble primary cell batteries often have a nanomaterial sticker on the side. In this respect, nanomaterials have entered the materials supply chain and are no longer regarded as special.

However, there is a strong argument that graphene – now arguably the most popularly known nanomaterial – has still a long way to go to fulfil its commercial potential. There are two soft issues which I believe are subtle but vitally important – vision and communication. It took a visionary to open up the concept of exploiting the nano dimension when, in 1959, Richard Feynman gave a talk entitled Plenty of room at the bottom. Around 40 years later, carbon nanotubes were commercialised, and ten years after that, graphene was isolated. The vision we now require is to convert the potential uses for graphene into products through technology. 

Graphene, in its basic form, is the first truly two-dimensional material comprising a sheet of carbon atoms, and is another allotrope in the carbon family. Its discovery has had a significant impact on scientific thinking, opening up the investigation into possibilities for hybrid layered variants or other 2D materials, and exemplifies the importance of a visionary approach to materials science. The global importance of graphene is illustrated by the worldwide patenting activity – the IPO report Graphene: The worldwide patent landscape in 2015 revealed that the worldwide dataset for graphene comprised around 25,000 patents, spread across 43 countries.

Overcoming commercialisation issues 

I am focusing primarily on the particulate form of graphene, which has widespread potential application in engineering and does not suffer from many of the usual issues that prevent commercialisation. Firstly, unlike many exotic materials, there is no supply problem. Graphene has multiple sources, such as exfoliation of mined graphite, or via CVD processing of a carbon precursor such as methane. Secondly, the list of potential applications is virtually endless. Thirdly, there are no identified health and safety issues outside of standard procedures for handling of particulates. 

However, as with all new materials, entering the marketplace is no trivial matter, and specific challenges exist. The first challenge is that, at the moment, every manufacturer of nanoparticulate graphene produces a different graphene product. In the academic and scientific world, many researchers have based their work on graphene produced in their own labs and not using a commercial product. This makes comparison of scientific data from different scientific sources more complicated. Of course, many industrial development projects have opted for one manufacturer and so use material from one supplier to ensure consistency of supply, but this in itself will not solve the generic problem in the long term.

This is a problem of communication. To overcome this challenge, I propose that there is an urgent need for a system of classification. Taxonomy might sound a very prosaic matter, but the word ‘graphene’ is used in common parlance to describe a huge range of materials from a single sheet of carbon atoms, to graphite particles and even graphene oxide. Classification or nomenclature is a hot topic of debate and is currently vexing a good many committees and technical bodies – each with a different perspective and end-goal.

The issue with nomenclature is that it is either so low level that it achieves nothing, or tries to include too much information and becomes unwieldy and impractical, so falls into disuse. My starting position would be from the perspective of the commercial supply chain, to develop a classification system that assists and promotes business – a working level approach. If we assume that graphene commercialisation is in its infancy, then, presently, the majority of users are prospective and need a system that facilitates market entry and speeds up the commercialisation process. If a working level classification only covered 80% of materials available, even that would be a great improvement to help business. 

A proposal

I would suggest that a usable classification system for particulate materials would be two-tier. The first tier would be the mandatory primary classifier to distinguish the material type, such as ‘G’ for graphene and ‘GO’ for graphene oxide, with the letter ‘P’ to denote particulate material (‘GP’ for particulate graphene and ‘GOP’ as particulate graphene oxide). If, in the future, the quantum dot form of graphene becomes a commercially significant variant, that might be denoted ‘GQ’, and so on.

Next, the source or processing route of the material is a commercially useful piece of information. At present, the two major processing routes are exfoliation of mined graphite, or bottom-up formation from a precursor such as the CVD process. This information could be denoted by a single letter, such as ‘M’ for mined and ‘C’ for CVD.  Since graphene oxide is primarily produced from mined graphite, I suggest that this would be taken as read and not require an additional letter. Under this system, the top tier of information would look like the following:

GPM – graphene particulate from mined graphite

GOP – graphene oxide particulate (by inference from mined graphite)

GPC – graphene particulate from CVD processing

The second tier of information would start to scope the major parameters of the graphene particulate. The parameters most useful commercially are the following –

Average diameter range

Average thickness range (or number of layers)

Surface chemistry (functionalisation)

Proportion of graphene in mix

How to represent this in a manageable format is a challenge, but this should be left to manufacturers – it would be a sign of a manufacturer following best practice if they provided this information to prospective customers in their data sheets.

The added benefit of a nomenclature helps customers to identify which companies have actually classified their material, and to help set up product trials to compare the performance of different material variants from the same, or different suppliers. This working-level characterisation would be a good starting point to allow end users or supply chains to speak the same language.

Stimulating applications

All conversion of science into technology requires investment. The UK Government has committed £90m to institutes such as the National Graphene Institute at Manchester and National Graphene Centre at Cambridge, and this provision of infrastructure is vital. Converting a raw material into a product is not a trivial task. 

Converting a nanomaterial into a product is even more difficult, but the potential rewards of nanomaterials are finally being seen in commercial products. The development of ‘Catapult’ centres in the UK is a very important bridge between academia and industry – akin to the Fraunhofer institutes in Germany.  Funding for applied research projects is now top priority in order to make use of this infrastructure, and accelerating commercialisation of university research.   

We now need to focus on product development, which in the nanomaterials world generally includes new process and intermediary product development. As proposed above, this is where a visionary approach is important. Products come out of ideas, not just from scientists but also inventors, creative and marketing departments, after which the vision has to be converted into a business case for investment. 

The case for the use and benefits of nanomaterials is often not a simple concept to envision, and so good communication between the different stakeholders is vital. As one contribution to this process, the IOM3 Nanomaterials and Nanotechnology Committee is setting up regular discussion meetings under the banner ‘Café Nano’. The first of these themed meetings, which will provide a forum for all interested parties, including scientists, designers, media, potential end users and investors, will focus on graphene and feature Andrea Ferrari, Professor of Nanotechnology at the University of Cambridge.

In my opinion, a visionary approach making the most of cross-disciplinary communication is a winning combination to bring the benefits of graphene into manufacturing and wealth creation. Communication has a vital role to play and, in the case of graphene, to overcome the confused terminology. The ‘working level’ classification system proposed here is open for judging (and tweaking) by the industry to develop a weight of opinion which becomes standardised. 

Two very different morphologies

It is important to realise that the word is used to describe two different morphologies – graphene nanoparticulates and film graphene. 

Film graphene is being investigated mainly for use in electronics as a conductive film on display screens, to replace materials such as indium tin oxide, and also for thermal conduction in applications such as LEDs. New electronic devices based on graphene substrates rather than silicon are an exciting area where hybridising layers of graphene and materials such as boron nitride show promise as device sensors.   

Nanoparticulates are widely used as additives to polymers, rubbers, coatings, ceramics metals and engineering fluids. Relatively large commercial volumes of graphene nanoparticulate could be used in all these areas. Graphene nanoparticulates are colloquially differentiated between few layer graphene (FLG) or many layer graphene (MLG). 

The IOM3 Café Nano series of discussion events will commence in October at IOM3. For more information, visit www.iom3.org/event/cafe-nano