Powerful things often come in small packages and nanosized molecules are some of the smallest. Demand for carbon nanotubes and graphene-based materials is on the rise given the highly specialized, value-add role they play in diverse applications, including electronics, smart clothing and in safeguarding the environment, particularly our waters.
Given their abrasiveness and tendency to agglomerate, carbon nanotubes and graphene are difficult to break down and reorganize into usable chains. However, once this is achieved, they deliver exceptional electrical, thermal and mechanical properties. We sat down with Dr. Silvia Grasselli, Head of Process Technology Homogenization at GEA Italy to find out how GEA technology is helping bring these exciting materials to market and what’s driving demand, which is expected to reach an estimated US$2.86 billion in sales by 2025.
What are carbon nanotubes and graphene and how are they used?
SG: If we just take a step back, ‘nano’ is a Greek word meaning ‘dwarf.’ A ‘nanometer’ is one billionth of a meter – equivalent to one thousandth of the width of a human hair, which means these particles are not visible to the naked eye. A carbon nanotube is a sheet of graphene, basically a hexagonal lattice of carbon, that develops in cylinder form and is either single- or double-walled. A graphene is a 2-dimensional single layer of graphite consisting of a single or mono atomic layer of carbon atoms arranged in a hexagonal pattern. Graphene is the fundamental structural element of carbon nanotubes and is the most durable material known to man; it is also extremely malleable and elastic. Given that is only one-atom-thick, it is nearly transparent and is an excellent electrical and thermal conductor.
With a tensile strength 50 times higher than steel, carbon nanotubes (CNTs) are extremely strong, but also very light-weight. CNTs and graphene share many of the same properties (e.g., good electrical and thermal conductivity) and therefore compete with one another for use in many of the same applications – such as in electronic devices, like computers and mobile phones – which may include CNTs or graphene, or a combination of both, in their components. These nanomaterials also provide structural reinforcement in cars, airplanes, bikes and even tennis rackets. And their excellent absorption qualities have proved effective in cleaning up oil spills. Likewise, they are showing promise in breaking down microplastics into components that are safer to the environment.
What is GEA’s role in producing CNTs?
SG: While the world has known about CNTs and graphene for several years, they haven’t been used to their potential. This is in part because they are abrasive, have the tendency to agglomerate and tangle, and as a result are difficult to break down and restructure. To achieve this, GEA has patented a process combined with a unique configuration of its homogenizers, which use high pressure to break down the nano-molecules without damaging them, and in parallel, ensuring there is no downtime in the production.
The beginning of the process involves dispersing the powder in a mixture containing mostly water. From there it enters the homogenizer which breaks up the agglomerates, separates them and then places the nanotubes, one after the other, to create a linear structure. As a result, the surface area is increased which promotes greater transmission or insulation, for example, in electronics. This is the most efficient way to disperse and disaggregate the clusters into single walls, allowing for a robust and scalable manufacturing process that delivers high quality and consistent products, which as a next step usually involves embedding them in liquids or resins.
Are these materials safe?
SG: Integrated in products, such as electronics or embedded in clothing, end-users are not at risk from CNTs or graphenes. In powder form, however, carbon particles must be handled with care and not inhaled. By connecting more of the individual processes, the handling of these powders can be minimized or even eliminated. In an EU consortium running from 2006 to 2010, GEA and 22 partners explored how to more safely fabricate and further develop nanoparticles. A key finding in their work showed that by using GEA’s spray drying technology, they could greatly improve the safe handling of these powders because this processing step turns nanoparticles into larger microparticles, which, given their size, do not become airborne. And yet, they still retained their unique properties.
In addition to investigating the process for several years with customers, we’ve also partnered with the Italian Institute for Technology, which is conducting trials using one of our laboratory units, to further develop the safe use of CNTs and graphene across diverse applications. As a result, our learnings can be directly applied, which is very efficient and a major benefit to our customers.
What are key drivers behind the increased usage of CNTs and graphene?
SG: Both are already highly valued and will become even more so as time goes on, particularly given that industrial-scale production has increased, making them more commercially viable. Likewise, the massive focus on the environment and the very positive results achieved in using this technology to clean oil from water and break down plastics will be important drivers, although these applications are still in the formative stages.
They are increasingly being used in coatings and composites within the plastics, construction, automotive, batteries, energy, aerospace and metal industries. For example, electrodes made with carbon nanotubes are ten times thinner and offer nearly 100 times higher conductivity as compared to amorphous carbon electrodes. Growing demand for lithium-ion batteries with higher conductivity in electric vehicles is also expected to open new avenues for carbon nanotube market growth. And, of course the increased usage of electronics and various devices will continue to drive a lot of the demand for these materials as their structure and properties are ideal for applications involving the efficient transfer of data, which businesses and consumers now expect to happen at lightning speed.
Given their special qualities as non-conductors and insulators, as well, CNTs and graphene have reduced the footprint of our devices and technology centers. Servers, for example, no longer require entire rooms with fans, but can now be contained essentially within a small box.“– Dr. Silvia Grasselli, Head of Process Technology Homogenization, GEA Italy
How are GEA customers using these materials and what industries and applications are involved?
SG: As mentioned, we’re cooperating with the Italian Institute for Technology, which is using GEA homogenization technology in trials to further effectively and safely develop nanotubes for use across diverse applications. Most recently, we published our combined findings on the building of functional nanocarbon paper substrates as a more sustainable alternative to those made from plastics and metals. This is an important step for possibly tackling electronic, or e-waste, by making it more recyclable and easier to manage.
We have customers throughout Europe and Asia who are providing CNTs and graphene-based products for use in the electronics industry, which includes batteries. And because of their technical properties, these materials are speeding up data transfer while also reducing the size of server rooms and devices given their tremendous insulating capacity, which minimizes heat transfer and therefore damage caused by heat build-up. Via our partnerships, we’re able to improve and tailor our homogenization equipment and processes; the result of one these led to an important patent for GEA and a better machine and product results for the customer – a win-win.
One of our chemical engineering customers has developed several graphene-based products; for example, some have barrier properties for coatings and paints; act as performance additives in lubricants or improve thermal conductivity in composites and plastics. They also have products that are used in packaging, in molding and 3D printing. Another GEA customer has developed a process for integrating graphene nanoplatelets in clothing, including active wear and footwear; as the body produces excess heat in certain areas, this heat is distributed around the clothing, making more efficient use of it by keeping other parts of the body warm, while minimizing static and friction. And as already mentioned, graphene-based material is being used to support oil-spill recovery, as well as wastewater treatment. In fact, this technology allows for the reuse of adsorbed hydrocarbons and adsorbent oils.
What can the industry expect from GEA when it comes to homogenization, CNTs and graphene production?
SG: By improving the design and durability of our homogenizers, GEA has helped bring down the total cost of ownership when it comes to producing CNTs and graphene. This was not an easy feat, given the material caused near immediate erosion of homogenizer valves – within 24 hours. Today, we’re able to partner and support customers across diverse industries in developing and producing these materials more efficiently.At our Process Technology Center for Homogenization in Parma, Italy, we’re able to provide customers with lab and pilot testing, as well as expertise to support product development, which includes cost-analysis and scalability. This, combined with customer-site support, helps minimize the customer’s investment risk while ensuring successful launches.