In the Winter 2011 issue of BEST, Rick Howard commented that a Google search for “nanotechnology” and “nanotech” resulted in nearly 17 million hits. A search for “nanotech” today will result in 284 million hits. Vic Giles spoke at AABC with David Arthur, CEO of Chasm Advanced Materials, to find out what the company is doing differently to other carbon nanotube (CNT) producers.
BEST: What is the background of Chasm Advanced Materials?
David Arthur: Bob Praino and I co-founded Chasm Technologies in 2005 as a consulting business and we helped our clients develop and commercialise advanced materials. We found over the years that a lot of those projects involved CNT materials and coatings. Whether they were roll-to-roll coated, printed, or whatever, they were the combination of those two areas. Bob is an expert in coating technology and my background is material science.
We coated onto a variety of substrates but often, in the earlier years, it was coating onto clear plastic films to create transparent, conductive materials. There’s a long list of materials that are optically transparent. There’s a long list of materials that can conduct electricity. There’s a quite a short list that can do both well.
What are the applications for your transparent materials?
Most transparent conductive film materials are used in touchscreens and solar panels. Our current focus for transparent conductive films is transparent heater foils for automotive safety sensors. This enables the safety sensors to work properly during inclement weather. And the second area of focus for transparent conductive films is transparent antennas that can be attached to glass in vehicles and buildings for enhanced wireless communications.
A lot of our activity centred in that area and in 2015, 10 years in, we had a very successful consulting business. We never had to look for business and were profitable every year.
How did you get involved with carbon nanotubes?
We decided to make a bold move and we acquired the assets of our largest client, who was a producer of CNTs. So, now we are proud owners of a carbon nanotube factory in Norman, Oklahoma, which is where that company spun out of the University of Oklahoma.
We changed the name of the company at that time to be Chasm Advanced Materials to reflect we’re no longer doing consulting but were putting our resources towards developing and commercialising our own advanced materials products.
Our CNT additives business is where we started off pursuing reinforcing additives for concrete. CNTs are the strongest materials known; they’re also tiny, about 50,000 times narrower diameter than human hair. They are about 10 microns or so long and 10 nanometres in diameter. If you have high aspect ratios, above about 100, it makes it a very efficient reinforcing material, replacing steel. With concrete, we’re starting by targeting the tiny amount of one kilogram for one metric ton – you can double the strength and double the stiffness.
Why would it be so valuable to eliminate steel in a structure?
You want to eliminate steel because it corrodes, it increases the complexity of fabricating concrete, and reinforced concrete collapses spectacularly over time. Also, CNTs are part of the solution for greener concrete. What people don’t appreciate is 8% of global carbon emissions are associated with cement production. It is very cost sensitive, and you need to be able to make a massive quantity of CNTs because, even at low loading, there are lots of metric tons of cement. So, we developed the lowest cost, most scalable method of mass-producing CNTs.
And we asked ourselves the question: what other industry would want to buy such large quantities in addition to the cement industry? And that’s when we concluded that batteries would be a good target. CNTs in lithium-ion batteries used to be a ‘nice to have’, but now they’ve transitioned to a ‘need to have’. If you want to have the highest performing lithium-ion batteries, you will want to put CNTs in the electrodes of those batteries.
How do stiffness and strength benefit batteries?
One example is in silicon anodes where there is the swelling, and silicon isn’t all that electrically conductive. CNT additives provide very efficient conductive pathways, but also provide a mechanical scaffolding, if you will, to absorb the stresses and provide mechanical reinforcement. In that architecture the CNTs are multifunctional.
In some of the more traditional NMC type cathodes, the CNT is primarily an electrically conductive additive. Because it conducts electricity more efficiently, you can not only reduce the internal resistance of the battery – which can help for faster charging and discharging – but you also put less conductive carbon in to make more room for active material.
So, you can get an incremental increase in the energy storage capacity; make it more practical for higher rate charge and discharge. And so that’s the motivation for using CNTs in general in the battery industry.
How do you significantly reduce manufacturing costs compared to your competitors?
Most of our competition use a manufacturing platform called a fluidised bed reactor. This is a vertical tower with a high volume flow of carbon-containing gas that comes through the bottom, and it takes a powder catalyst and makes it look like a boiling bed of powder, called a fluidised bed. The most common type of carbon containing gas used is ethylene, which is what we use also, so that’s not a point of distinction. But that production platform needs to be very large to produce a certain output of nanotubes. The equipment investment can be expensive, and the footprint rather large in that plant.
We’ve embraced a rotary kiln; rotary kilns are used at huge scale to produce cement. So, we have a much smaller scale rotary kiln reactor that we have tailored to grow carbon nanotubes. And so, for the same amount of product output, we have a much smaller piece of equipment, and we estimate it’s about five times more capital efficient than the fluidised bed. That becomes very important when you try to drive production to the scale that we are bringing in, which is 1500 metric tons a year per CNT reactor.
Most of the CNT production machines in the world today are low hundreds of tons per year. I think the biggest one that we’ve heard would be about a third of the size of what we’re bringing online in the second half of next year.
And what sort of volume does a gigafactory require?
It depends on what loading of CNTs, so I’ll give you a generalised answer. I would say from low hundreds of tons to high hundreds of tons. One of our reactors could more than adequately support a gigafactory and could realistically support multiple.
And for concrete 1500 tons is about right, although we might have to build a bigger one down the road. We think it’s about the right size for supporting gigafactories and it’s good for starters.
What are the advantages of your rotary kilns versus fluidised bed reactors?
The most striking advantage of our rotary kiln platform versus the fluidised bed is much less capex for scaling, which translates into much less depreciation expense on the product costing. On the other side of the equation, we don’t require such high gas volumes as the alternative to keep the particles fluidised. Our number one opex cost is the gas – we use less gas, and we have a very high conversion of that gas into products.
How are the carbon nanotubes generated in the kiln?
We put in a catalyst powder, which is a metal oxide material that looks like very fine grain beach sand. We decorate it with metal in a proprietary process and so we make our own catalyst. These very fine particles are delivered to a rotary tube furnace and when the ethylene gas hits those particles at the temperatures of the rotary kiln, the ethylene molecule decomposes – ethylene is made from carbon and hydrogen atoms. The carbon atoms are donated to the catalyst site, which results in crystallisation growth of CNTs. CNTs grow off these catalyst particles (Fig 1). There are many CNTs that are growing kind of as a bundle. And hydrogen is a by-product.
Do you have any plans to use the surplus hydrogen that is generated?
What we are designing in our next generation reactor is to recycle any unreacted ethylene back through the reactor, and then take off the hydrogen. We can repurpose that hydrogen and use it for other things. And the simplest thing we’re thinking is to use it to heat the kiln. Right now, our next generation is still an electrically heated furnace, but the type B of that furnace will end up using the hydrogen as a clean fuel, which will make our process even more sustainable.
What temperature is the furnace running at?
Between 600 and 700°C, so it’s not that hot. You’re much higher than that for instance in a rotary tube furnace for cement production. Down the road we’ll have the ability to use a clean fuel that essentially is free because it comes from the gas.
Are the CNTs single or multiple wall?
We produce single-wall CNTs for printed electronics applications (transparent heaters, transparent antennas) and advanced membranes (reverse osmosis membranes for water purification and desalination). Chasm produce multi-wall CNTs for lithium-ion battery applications (conductive additives for cathodes and anodes) and cement applications (reinforcing additives for more sustainable concrete).
Can you tell us a bit more about the structure of the CNTs – armchair, chiral or zigzag?
Our CNTs have a distribution of these structures. For single-wall CNTs, we do have the unique ability to control this nanotube wall structure (aka chirality) during synthesis. This can be important for printed electronics applications. For multi-wall CNTs, it is not important to control chirality. However, we do control other key multi-wall CNT parameters such as diameter, number of walls, morphology, purity and crystallinity.
What is the current health and safety status of CNTs?
The number one health and safety concern for CNTs is the inhalation hazard. To address this, Chasm and other CNT suppliers are establishing supply chain designs where CNT materials are delivered in product forms that are easy and safe to use. In the battery industry, CNTs are typically supplied to gigafactories as dispersions or pastes that have the CNTs pre-dispersed in liquids. In the printed electronics industry, CNTs are typically supplied as inks or as films.
Is there a special technique for getting the carbon nanotubes into the battery materials?
Yeah, good question. First, for the battery application, we dissolve the metal oxide that the nanotubes have grown on, and we call that chemical purification. The industry either uses chemical purification or thermal purification.
We use chemical purification because the thermal purification typically results in damage to the CNTs, and we don’t want to take that trade-off. We have a wastewater treatment process that essentially has no hazardous waste streams. It’s very sophisticated design and we’ve been using that for years. So that extra step is done for battery materials that is not done for cementitious materials. They don’t care because cement is comprised of a lot of metal oxide materials.
After growing and chemically purifying the CNTs, the next key step is dispersing them, and that has been another commercialisation barrier for CNT products. It’s difficult to disperse these tiny particles, they like to clump together. Typically, they’re grown in a bird’s nest structure and so they’re so entangled – you’ve got to break them to disentangle. In our process we engineer the growth to deliver a bundle structure (Fig 1). So, when you disperse them into a liquid, they just kind of peel apart. They don’t require as much dispersion energy and we can retain the length during the dispersion process and that length is important to maintain the high aspect ratio.
Typically, the users of the CNT materials will want to buy them as a dispersion for ease of use. They don’t want us to pass the burden of dispersion to them.
What size is the company and what are your development plans?
We are 35 people strong. We have a facility in Oklahoma. We have a facility in the Boston, Massachusetts area. That’s our headquarters and application development centre.
Our business model is we are investing in expanding our manufacturing plant to house up to three of these 1500-ton reactors, and a chemical purification line for the battery industry. We can do dispersion samples, but we’re likely to depend on a channel partner to do that step. And we’re seeking partners that are already serving the cell producers maybe with dispersions of other carbon materials, to have them create dispersions from our materials. We will pass on the recipe that we know works and rely upon them to serve the cell producers.
We’re a US company, so naturally a home market gives us a bit of an advantage. We’re also targeting Europe, but our first reactors will go online in the United States.
Is there funding from the Inflation Reduction Act?
We’re seeking, and hoping to receive, such funding. And for Europe Mike Fetcenko, our chairman, who’s from the battery industry, made it very clear in his talk at AABC, to serve the European market will probably involve a joint venture and/or licensing partners that will allow that market to be served locally.
The Atlantic Declaration between the US and the UK is intended to boost trade, so maybe we’ll see something in the UK?
The UK is a very logical choice and that would perhaps be a good stepping stone into Europe. We’ve had discussions with some players over there, but at early stage. I think it’s going to be important for us to put this demonstrator plant in Oklahoma, let the strategic partner candidates come in, kick the tyres see how real this is. And then hopefully we can shake hands and move forward.
When we formed the company in 2005, we started working in CNTs and we got caught up in the hype cycle like everyone else did. Every problem on earth could be solved by CNTs and our little company could take over the world by itself, and both of those statements are not true. There are really good applications for CNTs and there are other ones that don’t make as much sense. We think we’re targeting the right ones and we think our partnering strategy is a healthy one.
