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AMN8 2017February 13, 2017

AMN8 Queenstown: talking superconductor sandwiches at 25,000 feet

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Charles Anderson is in Queenstown for AMN8 – the advanced materials and nanotechnology conference hosted by The MacDiarmid Institute. In his first blog from the event, he enjoys a heaven-sent introduction to the field from Ben Mallett on the flight south.

The flight from Christchurch to Queenstown is full, says the cabin attendant. But as the young man sporting the sandals, white rimmed glasses and several days’ stubble sits down, there is still plenty of room.

There is a nod of acknowledgement. And then, the small talk. Usually on planes this is confined to the basics of one’s day, one’s imminent plans. But today it evolves into a world I know next to nothing about – solid state physics.

“What brings you to Queenstown?” he asks.

“I’m heading to a conference in a field that I don’t really have any idea about,” I answer.

“AMN8?”

He could have been a backpacker but it turns out that Ben Mallett is a doctor of physics, who is based in Auckland as the Rutherford postdoctoral fellow.

AMN8 is the yearly conference organised by the MacDiarmid Institute, which brings together 500 scientists from around the country and from 35 countries around world to discuss the latest developments in the fields of nano and materials science.

I am here to try and bring some insight into a world little seen or understood beyond those in the science circles. I am an outsider trying to relate this world to a greater New Zealand population.

For the past several weeks I have interviewed several scientists who will be speaking at this conference.

Their work ranges from understanding how nano sized particles can be used to better deliver chemotherapy to cancerous cells to changing the future of the energy sector by developing efficient solar panels out of newly discovered materials.


Read Charles Anderson’s interviews with AMN8 attending scientists:
Zoom in. Keep zooming. Don’t stop. On New Zealand and the nano-revolution
Unpeeling the nano onion: Silvia Giordani on the potential for a massive, tiny breakthrough in cancer treatment
Henry Snaith: how a miracle mineral may hold the key to a solar energy revolution
Amanda Barnard: how tiny diamonds could forever change the face of medicine
Rachel Segalman and the incredible possibilities of the new thermopower generation


So Ben is an ideal soft introduction to this world. He is generous with his explanations and unintimidating. He is on a budget and when we land will be checking into a bed and breakfast out of town. He hopes to rent a bike and cycle into the conference each day.

As we pass over the Southern Alps, Ben says events like AMN8 are invaluable to scientists. They can bring people together who may be working on different problems but could bring insights to each other’s work.

His work, he explains, is with superconductors – materials that can conduct electricity with zero resistance.

In normal conducting materials an electrical current always faces resistance. This creates not only wastage but potential disaster if a material gets too hot. So superconductors open up a world of possibilities, Ben says.

“This means you can do things with them you can’t do with normal metals – you can only do them with these materials.”

One example is MRI machines.

“The way they take an image is that they need a strong magnetic field.”

The way you create that is not with normal magnets but with a coil of wire that is charged with a “dirty big current”, as Ben puts it.

If you did this with normal conducting materials the whole thing would melt. So instead a superconducting wire is used.

Inflight nano-instructor: Ben Mallett. Photo: Charles Anderson

Normal conducting metals work better when they are cooled. But even when they are cooled to their lowest possible point they will still have some resistance.

The resistance of a superconductor, on the other hand, will drop to zero when it is cooled to certain point. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source.

But to cool normal superconducting materials is very expensive. To do this scientists use liquid helium – a non renewable resource which is running out.

So Ben has started working with another superconducting material which is less well known. It doesn’t need cooling down as much.

Named the particularly unexciting YBCO (which relates to the elements it incorporates in the periodic table), it can carry a very large current and can work at a very high temperature.  These are two of the key characteristics of an effective superconductor. It is also relatively stable, non toxic and all its materials are relatively easy to come by.

But what Ben has started to do is experiment with the material by sandwiching it between two slices of magnetic material.

“When you sandwich it together then you get some completely new behaviour in the superconductor. It’s like if you have bread that’s sitting by itself and some ham alongside it but then when you put together you get something completely new.”

It becomes a superconducting sandwich.

In this formation YBCO becomes a better superconductor in a magnetic field.

“That’s never been seen before.”

It also becomes a better superconductor in an electrical current.

“That too hasn’t been seen before,” Ben says. “It’s exciting and asking to be explained and used.”

As we land he talks about how his work could be applied to the real world. It could be applicable, for example, to next generation giant wind turbines that need smaller motors to power them or else they might topple over. But while he has those sorts of visions in mind he knows that it is a long road before any innovative science becomes ubiquitous in the real world.

His real concern is that science is answering problems that the real world has.

“There is no point in doing science that people don’t need,” he says. “Sometimes I think there is a gap between what we do and what the real world needs. We need to get better at understanding that.”

We part ways at the airport but a short while later I see him at the conference venue. He found a bike.


This is part of a series of articles for the Spinoff about and from AMN8, The Eighth International Conference on Advanced Materials and Nanotechnology, in Queenstown from February 12-16 2017. For details on public events in Christchurch, Wanaka, Queenstown and Nelson, click here. This content series is sponsored by the conference’s hosts, The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.

 

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rachel-segalman

ScienceFebruary 12, 2017

The incredible possibilities of the new thermopower generation

rachel-segalman

By embracing the thermoelectric potential of polymers, Rachel Segalman is pursuing a new frontier in the use of power to heat or cool. A speaker at the AMN8 conference in Queenstown, she talks to Charles Anderson

Across the world, a huge amount of energy is expended heating and cooling spaces which people do not use. What if there were a way to shrink that space?

What if, instead of using electricity to cool or heat an entire space, you could create electricity from someone’s own body temperature? What if you could use this process to heat and cool your clothing? Or your chair? Or a blanket?

“We have electric heating devices such as electric blankets but if you could use thermoelectrics that are capable of both heating and cooling, a huge range of applications open up,” Professor Rachel Segalman says from California.

A cooling blanket could be used during surgery, for example, where the temperature of a patient is of the utmost importance to ensure they don’t suffer ailments such as strokes.

Segalman works with thermoelectricity – devices that use temperature differences to create power or use power to heat or cool. With that premise in mind, a whole range of things could be powered using the temperature difference between one’s own body heat and one’s surroundings – your cellphone perhaps, or a laptop.

To think in terms of thermoelectricity means you need to shelve what you think you know about how materials work.

Segalman says a good thermoelectric has a high electrical conductivity so that it can shuttle power in and out, but a lower thermal conductivity. This is very hard to achieve.

“Intuitively, we know that most materials that are thermally conductive are also electrical conductors,” Segalman says. “For example, a metal rod will both burn you if you touch it with something hot and shock you if you touch a live wire to it.”

Polymers are a special class of materials, she says. These can now be made as electrically conductive as metal, but do not allow heat to travel through them very well.

To explain the thermoelectric process, it is helpful to imagine a material that is not thermally conductive, Segalman says. If you make one side of this material hot and the other side cold, the hot side will create motion in the material’s electrons. These electrons will naturally “shuttle across” to the cold side. Since those electrons are moving through the material, this can create an electrical current.

In a thermoelectric material, electrons travel from the hot to the cold side. But the extent to which electrons do this is governed by the Seebeck effect, also known as the “thermopower”.

“Think of the thermopower like the strength of gravity,” Segalman says. “Flow water through a turbine down a 100-foot hill on earth and you will get electricity.”

However, if gravity were twice as strong on earth you would get much more electricity from your turbine.

This is the same for a given temperature difference, she says. The stronger the thermopower of the material is, the more electricity you will get from the device. Get the right material, make one side hotter than the other, and you will get electricity

The effect also works in reverse, she says, meaning if you were to send an electric current across the material, one side would get cold and the other hot.

Since the 1950s scientists have exploited this process mainly using a material called bismith telluride. Its thermoelectric qualities appear in everything from NASA space technology to silent refrigerators. But it is notoriously expensive and hard to process.

So Segalman started looking at different materials that had been posited as potential replacements. Curiously, one of the best materials that she found to create such a process were polymers or plastics.

“Polymers are inherently thermally conducting,” she says, “because they are messy, disorganised materials and heat generally travels better through crystalline materials.”

They have low thermal conductivity and high thermopower but they lack electrical conductivity.

“If you can make a polymer that has sufficient electric conductivity that makes it interesting.” So that is what Segalman is trying to do.

In 2000, a team including New Zealander Alan MacDiarmid, won the Nobel Prize for chemistry for their work showing how to create high electrical conductivity in polymers.

Segalman is now working to show how these materials can also be engineered to have a high thermopower so that they can be made into wearable, lightweight thermoelectrics.

She is a third generation chemical engineer. Her grandmother was an engineer in China at the beginning of World War II. Her mother was a biochemist. At a family reunion they discovered that 75 per cent of the family were either chemists or chemical engineers.

“It’s interesting, no one said to me you must be a chemical engineer because the whole family is.”

When Segalman was studying she wanted to be a doctor but her parents convinced her that pre-med as a college major wouldn’t be as much fun as engineering.

She could always go to med school afterwards. She didn’t.

She found the problem solving aspects of the field interesting and compelling.

Now, applied to the field of thermoelectrics, her ability to do just that could have big consequences for the future of how we source our electricity.


This is part of a series of articles for the Spinoff about and from AMN8, The Eighth International Conference on Advanced Materials and Nanotechnology, in Queenstown from February 12-16 2017. For details on public events in Christchurch, Wanaka, Queenstown and Nelson, click here. This content series is sponsored by the conference’s hosts, The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.

AMN8 2017