Magnetic Fridge
JB: This is Earth and Sky. Nanotechnology involves working with extremely small things – on the scale of just a few atoms.
DB: Some say nanotechnology will herald “a new industrial revolution” – a new way of creating the things we use around us every day. In the process, scientists are finding that – when you manipulate objects on very small scales – you create materials with new properties. For example, scientists have known for a century that – when you apply a magnetic field to some materials – they get hotter or cooler. But these natural materials take a lot of energy to heat up or cool down.
JB: Scientists are now creating nano–materials that exhibit magnetic cooling using less energy. Someday, this process might mean energy–efficient air conditioning for your home or car. Bob Shull at the National Institute for Standards and Technology is developing nano–materials at the heart of a new cooling system. NASA wants to use them within five years to help cool electronics on a space probe. Ten years ago, when Shull began this work, other scientists were skeptical.
Bob Shull: The initial response was, “This is not possible! You can’t get bigger effects by doing that! . . . There’s got to be something wrong” . . . But that disbelief has now become belief.
DB: Our thanks to the National Science Foundation – where discoveries begin. We’re Block and Byrd for Earth and Sky.
The following individual was interviewed for today’s show. Our thanks to:
Bob (Robert) Shull
Materials Scientist
National Institute of Standards and Technology
Author’s Notes:
When you hear the term “nanotechnology,” you might imagine tiny robots that flow through your blood stream unclogging arteries or fly around cleaning up polluted air. But most scientists say that kind of technology may be decades away, if it’s even possible. Much of the current progress is being made in developing new materials – materials that have special properties that aren’t found in natural materials.
The new materials that exhibit magnetic cooling are made in traditional ways – by mixing chemical solutions together and evaporating the water or by melting metals together. But the different materials in the composites form “nano–scale structures” – so it’s considered nanotechnology.
The new nano–composites that exhibit magnetic cooling might be useful in creating more efficient air conditioners for cars. It could also be used to cool electronics.
Bob Shull: “Most electronic devices work better at low temperatures – there’s less electrical noise and therefore they’re more sensitive. So if you’re creating heat, you want to get it out. And you also want to get it out by some technique which does not have many moving parts. You see a magnetic refrigerator does not have many moving parts. You’re applying a magnetic field and taking it away, you’re not moving anything. The technology for cooling normally requires this big compressor. So you have this thing – a vane or a valve or something that’s moving back and forth and creating a vacuum on one side and pressure on the other side to move things around. Up in space, those things wear out. Not real quickly, but within the lifetime of the spacecraft. And there’s no way you can go up there and replace it. So they don’t want to have things like that which have these moving parts.”
Bob Shull continues: “The other thing is they don’t want so much vibration. And these normal pumps create a lot of vibration, so that’s not so good either. So they really like the idea of magnetic cooling. And NASA Goddard – the people we’re working with – have developed a refrigerator, which looks like it’s working very nicely. And hopefully we’re going to be able to improve it even more. So that’s going to go up. And in fact, because of the success already, since the development of that actual refrigerator, NASA is looking at using the same sort of technology in other spacecraft.”
Shull has been at this for about ten years, but he says that still makes him a bit of a newcomer to this field.
Bob Shull: “In fact, I think that’s why we’ve been so successful in large part because we’re not encumbered by the prior state of art in some sense. That is, we weren’t constrained by only thinking in terms of what people had already been doing.”
Bob Shull: “So anyway, I think much of our success in this particular arena of magnetic cooling is because we’re relatively new to the field and we didn’t constrain ourselves to only thinking about paramagnetic materials or ferromagnetic materials, which is what people have been doing all along beforehand and started looking about at these newer types of “nano–composite” type materials and realized that there might be something here.”
Shull says there’s a lot of trial and error involved in making new nano–composite materials. And often a new material turns out to have different properties than are predicted. But that sometimes stimulates whole new areas of research.
