In the real world, its equivalent just might be vanadium. This silvery-grey metal was once used to construct some of the most celebrated blades in the world, including the Damascus Sword, on which George R.R. Martin based Valyrian steel. The swords were known to be so sharp that they could cut a “floating feather in half.”
And while swords are no longer the metal’s primary end-product, vanadium’s use in rechargeable batteries could position it for international reverence once more.
The shift to a low-carbon economy requires increasing reliance on renewable energy technologies, like wind turbines, solar panels and rechargeable batteries. Lithium-ion batteries are currently positioned to lead the market in rechargeable energy storage. Extracting enough of the minerals required for these batteries—including lithium and cobalt—in time to meet the Paris Commitments, however, may not be economically or politically feasible. Supply shortages are projected for both cobalt and lithium within the coming decade. In addition, there are ongoing concerns regarding the lack of transparent and responsible sourcing in the supply chains of both minerals.
Vanadium Redox Flow Batteries—or vanadium-flow batteries—could become a valuable substitute for lithium-ion batteries. Vanadium-flow batteries can be charged thousands of times without degrading, making them ideal for projects that require immense cycling. In addition to being long-lasting, vanadium-flow batteries are extremely durable and can hold immense amounts of energy. Vanadium-flow batteries also derive from a non-flammable material, making them safer and more reliable for large-scale stationary applications. These qualities make vanadium-flow batteries a legitimate, and in some cases superior, alternative to lithium-ion or lead-acid batteries for large-scale battery storage, especially for wind and solar power generation farms.
Currently, vanadium is primarily used as a steel alloy in products like cars, gears and jet engines. Its importance to the energy sector, however, is growing rapidly. In 2018 alone, the price of vanadium more than doubled, reaching historic heights. This accelerated growth in demand and price for the mineral made last year—for some—“the year of vanadium.”
The extraction and production of vanadium is largely concentrated in four countries: China, Russia, South Africa and Brazil. However, given the surge in demand, many mining companies in North America have revealed plans to invest in exploration or reopen closed vanadium mines in the United States, Canada and Australia. Energy Fuels, for example, announced plans to restart its vanadium production in Utah. And in March 2019, the Canadian company First Vanadium doubled the size of its vanadium site in Nevada. Recycling is also a significant source of vanadium, with as much as 40 per cent of total vanadium catalysts coming from recycled materials.
Vanadium-flow batteries have a low energy density, meaning they will most likely not replace lithium-ion batteries in mobile phones or electric vehicles. Their use for large-scale, stationary projects, however, could be a game-changer for the energy transition.
As we accelerate the ongoing energy transition and rely increasingly on renewable energy storage technologies, the transparent and responsible sourcing of strategic minerals will become even more necessary.
A low-carbon future is coming—and vanadium may play a big role.
Forging Valyrian steel – By Rebecca Pool
Does a real-life version of Valyrian steel, popularised by the Game of Thrones series, have the potential to revolutionise automotive markets?
If you ask any Game of Thrones fan about a Valyrian steel sword, their eyes will likely mist over as they describe its exceptional sharpness, strength, lightness and distinct ripple patterns. Ask Professor John Verhoeven, a retired Iowa State University metallurgist, about the real-life equivalent – a Damascus steel sword – and you’ll receive the same, wistful response.
“The surface of a Damascus steel sword has this beautiful distinct, wavy pattern,” he says. “But if you are able to cut one up and study its microstructure under a microscope you will see layers of carbide particles that look like the Milky Way; tiny white dots all clustered together.”
Be it fact or fiction, Verhoeven and many fans of the epic fantasy drama are dazzled by these legendary weapons. But for Verhoeven, his enduring passion follows a life-long commitment to solving the mystery of the Damascus steel sword.
Manufactured between the 3rd and 17th centuries, Damascus blades were prized for being so sharp they could cut a silk scarf in half as it fell to the ground
Manufactured between the 3rd and 17th centuries, Damascus blades were prized for being so sharp they could cut a silk scarf in half as it fell to the ground. Yet, as Verhoeven points out, the last swords were made in the early 1800s and the formula for the steel soon died out.
Reports indicate that the swords were made by forging small cakes of ‘wootz’ steel, manufactured in India. Here, craftsmen would melt iron and carbon-containing materials, such as charcoal, in a sealed crucible. The cooled and hardened ingots were then shipped to Damascus, where smiths would heat and hammer them to form the blade with its deadly properties and characteristic pattern.
Recreating Damascus steel
Verhoeven spent much of the 1980s formulating a method to replicate this process, with blacksmith Alfred Pendray. And come the 1990s, the pair were consistently making Damascus-like blades via a forging and cyclic heating process, and using a cast iron called Sorel.
“Al’s technique was similar to what we learned ancient people had used,” explains Verhoeven. “Still, I was unable to figure out what was going on right away, until 1996, when I realised this steel contained impurities of vanadium.” Indeed, as the metallurgist highlights, impurities, such as vanadium, promote the alignment of carbides during ingot forging, leading to the banding patterns.
Yet despite success, Verhoeven’s method never made it out of the blacksmith’s forge. According to the metallurgist, their process was labour- and energy-intensive, and, as he adds: “It’s just way too expensive to be commercialised.”
Developing a super malleable steel
But Verhoeven has hardly been alone in his hot pursuit of the Damascus steel sword. In the early 1980s, Professors Jeffrey Wadsworth and Oleg Sherby from Stanford University were developing ultra-high carbon, super malleable steels with great strength, ductility and toughness.
The pair manufactured ring components and bevel gears from their ultra-high carbon steel, and were convinced the material held great potential in structural applications, including ultra-high strength sheet materials for automotive applications.
Around this time, the researchers also realised their material compositions coincided with that of Damascus steel swords. Given this, they went on to hone the ‘Wadsworth-Sherby’ method which reproduced super malleable steels with coarser and aggregated iron carbides to produce the distinct banding.
Their results hit the headlines, and they reckoned they had shown that ancient Damascus steel swords could have exhibited super malleable properties. But, again, commercialisation faltered.
As Wadsworth, now president of US-based research organisation, Battelle, says: “Commercialisation of our ring components was intended by Sulzer Brothers of Switzerland, but the project was abandoned.
“We gave it hell of a shot and did everything we could, but we got caught up in scaling up costs,” he adds.
A new phase of development
So, does the failure of past commercialisation attempts leave wootz steel and Damascus-like components firmly on the historical shelf? Given ongoing interest, perhaps not yet.
In the last few years, China-based researchers from the Central Iron & Steel Research Institute in Beijing, have used metallurgical computational software to analyse Damascus blade data and proposed mechanisms for the breathtaking bands.
“It would be interesting to compare the properties of modern steels going into cars with those of ultra-high carbon steel and see if weight savings can be gained through the superior strength of these steels”
Meanwhile, researchers from Technische Universität Dresden, Germany, have used transmission electron microscopy to pinpoint carbon nanotubes in a genuine Damascus sabre, that they believe could also be linked to the banding.
Researchers at Mälardalen University, Sweden, have produced several knife blades while Damasteel, Sweden, produces ‘Damascus patterned steel’, for knife manufacture. And archeometallurgists from The Wallace Collection, UK, are using neutron diffraction analysis (a non-destructive scanning method that has high penetration into materials) to determine how several ancient blades were made.
For his part, Wadsworth is optimistic that, in time, the world will use Damascus-like steel for more than just the replication of ancient steel blades. “It would be interesting to compare the properties of modern steels going into cars with those of ultra-high carbon steel and see if weight savings can be gained through the superior strength of these steels,” he says.
Damascus swords had vanadium steel – Howie Firth
The mystery of a legendary type of sword is gradually being unlocked by scientists and smiths. A sword of Damascus steel was said to be so sharp that it could cut through a gauze kerchief – or a steel helmet – and so flexible that it could bend through 90 degrees without breaking.
But the last of them was made around two centuries ago, and no one could work out the secret of their manufacture – even with samples available to study.
Now, however, clues have been emerging, and one of the keys is the source of the steel – which came from India.
The source of the steel
It’s called wootz steel, from a word for steel in South India – ekku. India has had a reputation for its iron and steel for a long time – since around 300 BC, and some Indian steel was said to have been presented to Alexander. The ancient Greeks and Romans sourced steel from India, and the Arabs took it to Damascus, where it was used for many centuries. ‘It is impossible to find anything to surpass the edge from Indian steel,’ observed the 12th-century Moroccan geographer al-Idrisi.
The story of Indian steel can be found in a fascinating book available online, written by two leading researchers in the Indian Institute of Science at Bangalore, S. Srivavasan and S. Ranganathan.
Many researchers tried to find out what was the key to the qualities of wootz steel. Michael Faraday – the son of a blacksmith – brought in a master cutler and surgical instrument-maker, James Stodart to help him, and they tried adding various metals to iron. They found that noble metals such as platinum and silver did indeed produce a harder steel and they thereby laid the foundations of the technology of alloy steel making – but they could not reproduce the wootz qualities.
But a clue to the nature of steel had already been found by the Swedish chemist Tobern Bergmann – it’s the carbon content that gives it the familiar qualities of strength and flexibility. Today the carbon content of steel rises from around 0.1% (low-carbon steel) up to 1-2% (ultra-high carbon steel) – and an analysis of Damascus steel shows that its carbon content was up at around 1.5% – in other words, right up with the finest steels that we can make today.
The Indian steelmakers introduced the carbon from carefully-selected plant material, such as the bark of an evergreen shrub called Cassia auriculata (used in tanning), and the leaves of a species of milkweed. The reason why carbon from plant leaves is particularly good is that when green leaves are burned they also generate hydrogen, which helps the take-up of the carbon into the iron.
Reinforcing fibres
One of the ways in which carbon produces the qualities of steel is through the bonding or iron and carbon atoms to form a very hard substance called cementite (iron carbide). Very fine strings of cementite particles act like reinforcing fibres running through the body of iron. With the right mix of these strings, an ultra-high carbon steel can show superplastic properties – can be extremely bendable.
And in Damascus swords, the strings of cementite particles form up into bands that you see as the typical wavy pattern on the blade.
But to get the right amount of these fine cementite strings is very difficult. Too high a temperature will prevent their formation. One reason why Europeans failed to reproduce wootz steel was that they sought very high temperatures, up to white heat, in addition to their failure to get a high enough carbon content.
And the wavy pattern only develops during the process of forging – when the steel is hammered into a blade. Nobody was able to work out how the pattern formed. There was speculation that it could be caused by some kind of impurity, and substances like silicon, sulphur and phosphorus, all known to be present in ancient wootz steels, were tried – without success.
How the fibres form
Then the American materials scientist John D. Verhoeven had a breakthrough. He happened to take for his source of iron a material called Sorel metal. This is a type of iron with a higher carbon content than steel (around 4 to 4.5%), referred to as ductile iron. Sorel metal is produced from a large deposit of the ore ilmenite on the St Lawrence River in Canada, ilmenite being an oxide of iron and titanium. The titanium is taken out for practical uses, and the iron left behind is very pure.
But remarkably, one impurity in that source of iron turns out to be the secret of wootz steel. This is vanadium. In Sorel metal, its concentration can be as little as 0.003%. But that amount, when added to high-purity iron-carbon allows, can produce good banding. Titanium also contributes, but the big influence comes from vanadium.
It seems that the very small traces of vanadium somehow segregate out of the iron when it cools, and that these traces form very thin lines along which the cementite fibres can form. Iron in liquid form can hold more impurities than can iron when it’s solid. And so every time that molten iron cools, a very little of the impurities will be forced out of it, and the impurities build up like a string of pearls. Forging and hammering seems to concentrate the bands further, with Verhoeven working over many years with a blacksmith, Alfred H. Pendray. You can see photos of Pendray making wootz steel in the story that Verhoeven wrote for Scientific American.
So the vanadium helps the strengthening fibres of cementite to form, in just the right type of band structure, and careful forging and hammering builds this up into the well-known patterns of Damascus steel.
Going to an even finer level
But a further suggestion for the cause of the cementite fibres has come from a German team led by Marianne Reibold of the University of Dresden. They have examined a 17th-century Damascus sabre and found – cementite nanowires and carbon nanotubes. A carbon nanotube is an incredibly thin tube, so thin that its diameter is only one-millionth of a millimetre; its walls are formed of one-atom-thick carbon. This is the first time that carbon nanotubes have ever been found in steel. The image is beautiful.
The Dresden University team found that some of the nanowires of cementite were encased in carbon nanotubes. So, they suggest, the process of forming the Damascus steel may start with the impurities, which help the carbon nanotubes to form. The nanotubes act as a kind of matrix within which the cementite nanowires can form, and the nanowires develop into larger cementite particles.
Further, they say, it was known that the swordsmiths of old used to etch their blades with acid. This brings out the characteristic wavy light and dark lines. And in addition, they add, the acid would dissolve a very little of the surface, exposing the acid-resistant carbon nanotubes which would protect their cementite cores, and creating an effect of a myriad of tiny saw-like teeth.And so a whole new field of investigation is opening up, bringing out subtler and subtler properties of iron and impurities at a molecular and atomic level – to understand the skills of the ancient Indian steelmakers of more than two thousand years ago and the smiths of Damascus who turned that steel into the swords of legend.
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