Graphene: A matter of quality

Last year saw the world's first ISO standard for graphene being published which defines the terminology used to describe the material. Soon after, there were good practice guidelines for characterisation also released by the NGI and NPL. As a result, the industry is now able to achieve more robust testing and validation of graphene products. It is therefore perhaps worth considering what impact these tools for quality assessment will have on the rate of commercial adoption for graphene. As I will aim to outline in this essay, defining quality is harder than it appears and there are other critical components besides which must not be overlooked.

If you have been paying attention to the press coverage afforded to graphene in recent years, you may have noticed that much of the commentary and observation surrounding the progress of the technology has often highlighted certain hurdles that need to be overcome by the industry. None more so that the alleged constraints of available price and quantity of the material. Indeed, this has become something of a trope for graphene, with a lack of low-cost and large-scale production techniques frequently cited as the main barrier to innovation. Even in recent years one can point towards the following examples:

"Scientists are still trying to devise a cost-effective way to produce graphene at scale." - The New Yorker

"It has been hailed as a wonder material set to revolutionise everyday life, but graphene has always been considered too expensive for mass production"- The Herald

"The absence of cost-effective and scalable graphene manufacturing techniques is a major current challenge" - Journal of Nanoparticle Research

Others have at least noted that it is a quality issue as well: "The main challenge lies in manufacturing large quantities of graphene, in various formats, and at an affordable price, with effective yields and a purity sufficient so as not to impair graphene's desired chemical properties." - Deloitte

If we were to accept that maturity of the technology is simply a matter of getting all these ducks in a row, then presumably there would be a threshold for each that we could identify and aim towards. However, the challenges of commercialisation with any new material are not as straightforward as this.

Without even looking towards other aspects which impact commercialisation of novel technologies such as regulation, policy and toxicology, there are further factors which stem from the production method with graphene that should also be considered as important. Besides the aforementioned price, quantity and quality there is also consistency and processability to add to the list.

As I have argued before, the real bottleneck for the industrial adoption of graphene today can be seen to exist primarily due to the complexity of the supply landscape (and the market confusion this provokes) and the immaturity of the value chain. These two problems are derived in the most part from the inadequacies of the industry to fully address the issues of quality and processibility. To summarise:

- Quality has been hard for companies to objectively establish due to a historical lack of characterisation standards and further exacerbated by a myriad of vastly different products made available on the market each sold as "graphene".

- Processability has been a challenge to overcome as graphene has proven difficult to incorporate into other materials without the right know-how.

Particularly the challenge of quality has created the most contention. Let's examine all of the proposed key factors to see why this might be the case.

But does domestic capacity to supply graphene hold significance as an indicator of progress in the global graphene race? Here are three main considerations worth exploring:

Price & Quantity
Regarding the need to address scale and cost as presented at the start of this article, the suggestion implies that the market is experiencing prices too high and not enough supply availability. On closer inspection we actually see there is an abundance of supply with underutilisation from end-users, at a ratio of production capacity-to-consumption in the order of 10:1. In addition, most of the products available within this large supply pool are of low cost to produce, with many of these graphene materials now priced within touching distance of carbon nanotubes, at ~$100 per kg.

It is important at this point perhaps to delineate between the product types in the market, which tend to be conflated in the discourse. Whilst additive grades of graphene (nanoplatelets, nanoflakes) are now commercially attractive, the graphene thin films such as those produced by CVD remain expensive compared to alternatives. When graphene is reported as being very expensive, it is usually in regard to CVD material, but this context is often lost. CVD is only one (relatively small) component of the total market. Overall, there are 4 times the number of graphene companies focusing on the production of the material as an additive rather than as a CVD grown thin film. As such, we should not let the cost and scalability challenges of the CVD market overshadow or obfuscate the successes achieved with graphene nanoplatelets.

In respect of consistency, this has been a bugbear for companies looking to exploit graphene technology but have been concerned about developing new products with a material that may experience some batch-to-batch variation. Quality management systems can ensure a level of consistency between batches, but product specification changes can still occur over longer time horizons. For instance, as a consequence of scaling up production a graphene company may experience changes to the output or have to make compromises to the specification on economic grounds. Some processes are modular however which can mitigate against this to a certain extent. Also, as mentioned many companies are already past this stage of upscaling to low-cost, commercial quantities of supply.

In the case of processability, this can be understood as the ease and readiness by which customers can integrate the material into their own products. For this reason, we see many producers supplying material containing functional groups. About 1/3rd of graphene companies can readily supply graphene oxide for instance. Graphene oxide is more soluble in water and some organic solvents compared to pristine graphene and therefore has its processing advantages. There are market pressures which are driving the development and supply of ready-to-use product formats (graphene derivatives such as functionalised material and other value-added goods such as suspensions, masterbatches and concentrates) to address this need for processability by customers. According to Lux research, a trend is observed across the nanomaterials market where value added goods termed "nano-intermediates" generate the highest net profit margins in the value chain. The same is undoubtedly true for graphene. Graphene producers noticed this and have long since been moving up the value chain as a result.

Successful nano-intermediate products are application specific and based on strong IP. Due to the many different application areas that are open to graphene it has taken a while to develop this platform technology into a product strategy. Graphene companies have been understandably hesitant to focus fire on one particular product area at the consequence of creating a potential opportunity cost.

Unlike the other four main factors, processability can be addressed by external companies and partners besides the graphene producers themselves. Signs of market maturity in this regard will be exhibited when more companies are formed whose business models are centred on the production and supply of these intermediates. This will strengthen the business ecosystem for graphene. However, there must be investment to nurture new businesses in this component of the supply chain.

Perhaps the most controversial aspect to discuss about graphene is that of quality. This should be unsurprising since we have a supply base that includes a very wide range of different material types and specifications. Where each producer is trying to differentiate their particular product offering, the allure of a material branded as "high-quality" is one way to achieve position in the market. Even the use of the moniker "graphene" has been under dispute for certain product types. Especially those with a significant number of layers. Recently the International Organisation for Standardisation released their nomenclature which included a definition of a 2D material with respect to graphene, as being up to 10 layers (ISO/TS 80004-13:2017). Whereby the electrical properties effectively become indistinguishable from graphite above this threshold. The question remains though how to determine quality. At face value we might accept that good quality graphene means something like "high purity, low defects". But on further reflection this is not quite so satisfactory.

There are two common definitions of the word quality: The quality of something can be an attribute. The quality of something can also be the degree of its usefulness or worth. The two uses of the term should not be confused because an attribute alone does not necessitate worth. There is a common assumption with graphene that if the material specification that we are working with is the closest representation to the defining characteristics of the material (i.e. "that which is most like graphene" - monolayer, pure carbon and so on) then it will be the most useful. This is not necessarily true. If we want to establish the usefulness or worth of something, then we should measure and compare properties that relate to its intended use.

In order to assess properties of graphene products at all, we must have some kind of standard way to measure and compare against one product and all other similar products. Fortunately for graphene, a Good Practice Guide was recently published by the National Physical Laboratory (NPL) in collaboration with the National Graphene Institute (NGI), at the University of Manchester.

Although there are protocols for characterisation of the material so that an objective comparison between products can be made, we are still only establishing attributes and not usefulness or worth. Quality will therefore only become clearer when BOTH the markets begin to perceive certain specifications as being more useful than others for their applications AND graphene products can be easily compared. The market needs to demonstrate reliable performance of different graphene specifications across various end-product groups and application areas. For instance, the graphite industry has different specifications for use in electrode, lubricant, or refractory products. The carbon black industry has different specifications for use in batteries, rubber, or plastics. The determination of quality of material in these cases is not applied universally, but in particular to the intended use.

Furthermore, as this article began, for commercialisation of graphene there are several other key factors which stem from production besides quality, which must all be addressed together. For instance, a customer will look at quality relative to the price of the material. In other words, they will assess the value. This is a far more interesting measure for the market. It is why we see sales figures for graphene products despite many being of low "quality", because they are also of low cost. The customer only wants to obtain the highest possible improvement in their application for the lowest possible price. It does not matter to them if they do not use the best quality graphene.

A lot of emphasis can be placed upon quality in the marketing of graphene products, yet there is no entirely reliable way from this to determine the actual value of one product to another until they are tested in the intended application. This is why demonstrable results are so important to customers, they want to see trusted application data generated from using a particular graphene. Most customers do not specify the graphene properties they want, they specify the properties they want out of their application or product. This ties into the processability problem since both quality and processability are intrinsically linked to the resulting value for the customer. The performance of the graphene in the customer's product will depend not just on the material characteristics of the graphene used but also the way the graphene has been processed into the final product.

Ultimately the challenge of determining value from a customer perspective is an information problem. Any lack of information otherwise needed to make an adequate assessment or business justification by customers creates inertia. Simplifying the ability for end-users to establish which products and processes they should use for what purpose will help release this roadblock. This should eventually emerge from further R&D activity in the application space and education of the market - from specific use cases with reliable data to brand recognition and product confidence. Quality is important, but it needs to be viewed from the customer standpoint, as performance to requirements.



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