Open/Close Mobile Menu Open/Close Mobile Menu

Graphene 2014: Natural vs synthetic graphene: cost, quality and competition

By Emma Hughes
Published: Thursday, 08 May 2014

There are many types of ‘graphene’ emerging from laboratories towards commercial uses, produced via a variety of methods and yielding divergent properties and apparent value. A key issue for those hoping to make graphene from mined graphite is understanding the differences between natural graphite-route graphene and synthetically produced material.

Since graphene was first isolated from graphite by researchers at the University of Manchester, UK, in 2003 and their findings were published in 2004, scientific interest in this space has snowballed.

 
In the decade since its discovery, graphene has attracted
billions of dollars' worth of research into the best ways to both
use it and make it (source: Festival della Scienza). 
While much of the excitement rests on graphene’s apparently endless list of potentially revolutionary uses, on the production side, an intriguing question has emerged over which is a better source material – natural or synthetic graphite.

Speaking in the opening session at Graphene 2014 in Toulouse this week, Rod Ruoff, from the Ulsan National Institute of Science and Technology (UNIST) in Korea, noted that graphite-route graphene has the advantage of lower raw material costs when compared to chemical vapour deposition (CVD) growth of graphene on substrates such as copper.

CVD is currently the most commonly used way of producing the atomic layer of carbon, however it is not the only graphene synthesis method in use.

Some of these alternative synthetic routes could be more cost effective than the graphite-route and, in some cases, could also be preferable in terms of application properties.

One company championing a novel synthetic route is Applied Graphene Materials (AGM), a spin-out company from the UK’s Durham University, which floated on the London Stock Exchange AIM in November 2013, raising £11m ($18.6m*).

Claudio Marinelli, AGM’s business development director, told IM that the company is currently capable of producing 1m tpa synthetic graphene, but hopes to scale up to 8m tpa within 24 months, highlighting the increased demand from customers, which he says “come to us – not the other way around.”

Different types of graphene

There are two main ways of producing graphene, either by exfoliating carbon layers from a graphite source, or using a substrate, such as nickel or copper, to deposit a precursor that contains carbon through CVD.

The latter method produces an almost continuous film of the same size as the substrate, whereas the exfoliation of graphite provides nanoplatelets – graphene flakes, varying in size from less than a micron to few tenths of microns.

CVD graphene is a very effective electrical conductor, meaning it can be applied as an electronic device transistor, or as a functionalised sensing surface as well as transparent and conductive layers as a replacement of indium tin oxide (ITO) for touch-screen displays.

However, while both natural and synthetic films can be used in a number of applications, there are some advantages associated with the use of synthetic over graphite-route graphene.

“Through CVD, you promote the assembly of carbon atoms using a template in such a way that you end up forming a single or bilayer film of high quality graphene, which is very close [to an] ideal, infinite continuum layer of carbon atoms that we call graphene,” Marinelli told IM.

“This material is very high quality in terms of being close to the ideal definition of graphene and there is this continuity in play that allows for good application – especially in electronics,” he explained.

In addition, CVD graphene is free of the impurities often left behind by the process of exfoliating graphite.

Equally, however, there are limitations associated with using CVD material. For example, this type of graphene can only be manufactured in quantities limited by the extent of the substrate and several steps are required to lift the graphene film from the substrate for application.

By contrast, graphene nanoplatelets, which take the form of a black powder, can be produced in volume and can be readily incorporated in dispersions.

Yet, production of graphene nanoplatelets through graphite exfoliation is essentially a batch process and relies on graphite supply.

To exploit the application advantages of the nanoplatelets and improve over the graphite-based manufacturing method, AGM has developed a proprietary process for the synthesis of graphene that does not require graphite as a starting material.

Combining some of the benefits of CVD synthesis and the graphite-route, AGM’s method allows for large volumes of graphene nanoplatelets to be produced free of graphitic impurities in a scalable and very “green” process, Marinelli told IM.

This delivers a highly dispersible powder suitable for a number of volume applications, where AGM nanoplatelets can bring the desired material multifunctionality in terms of – for instance – enhanced mechanical, electrical and thermal properties.

“By virtue of being a small, fine powder, it is very much like an additive. We are all familiar with additives in polymers, solvents and paints, so it enters a range of applications through dispersion in a polymer or in a solvent. It can also be used in batteries or supercapacitors alongside activated carbon,” Marinelli said.

Again, however, there might be disadvantages of using graphene in a nanoplatelet format, as the material no longer exhibits the continuous properties of the CVD-produced film.

“This means that, for example, electrical conductivity is no longer continuous but [travels] through islands, so conductivity takes a bit of a knock back when using powders,” Marinelli said.

“Depending on how you produce your graphene, you will notice different properties and hence benefits, once you deploy that graphene in an application,” he added.

As a result of this, competition in the market is more complementary than competitive, as “there are some applications where other materials might be better than ours and vice versa,” Marinelli admitted.

What about price?

One of the most talked-about points when it comes to graphene is price. Not just production costs, which until mass manufacturing methods are optimised will continue to be expensive, but also end-market prices, which will remain high until production costs come down.

Marinelli told IM that, in terms of natural versus synthetic graphene, he does not see much of a difference in price.

“In the long term, methods for producing powders are intrinsically scalable, so I can see less constraint in terms of process, scaling up and reducing the cost of flakes, rather than continuous films,” he said.

However, Marinelli also admitted that the question of price is the most difficult to answer in relation to graphene.

“If the material delivers the advantages that we all hope it will, price will become irrelevant because the material is only used in very small quantities,” he said.

“Secondly, I would rather not set a price that limits the range of applications. Rather, I would like to try and explore an application that can redefine the price point for the final product, which provides advantages for the customer as well as for the supplier,” he added.

Marinelli also noted that, realistically, graphene is going to make its way onto the commercial landscape via high value products, at least to begin with.

Market share

While the different and as yet ‘ unstandardised’ types of graphene each have their own advantages and disadvantages, Marinelli believes that the future of this material will contain both graphite-route and synthetic producers.

“To an extent, we have a degree of overlap even among platelets applications,” he said.

“Perhaps graphite-derived graphene, because of the presence of graphite and transition metals, might be more suitable for electrical conductivity applications and other uses, such as inks and plastic electronics.”

“AGM’s synthetic graphene platelets might find greater acceptance in polymer composites, paints and coatings, lubricants and functional fluids, whereas other end markets are more suited to the film-type of graphene,” he told IM.

“I do believe that both [types of producer] will be very busy filling the requirements of customers in these areas,” he added.

To conclude, Marinelli stated that while no killer application for graphene has yet been rolled out, commercial production of the material is not far off.

“Purely from a statistical point of view, there are so many potential applications that have been proposed to us that some of these are going to come to fruition,” Marinelli explained.

“In addition, the diversity of these applications, combined with the multi-functionality of graphene, gives me a lot of hope that we will pretty soon find a home in the shape of a ‘killer application’,” he said.

*Conversion made May 2014



More like this