What are plasmas?

In this video, Professor Margaret Hyland from the Chemical and Materials Engineering Department, University of Auckland, defines the terms ‘plasma’ and ‘artificial plasma’. She then describes the types of plasmas used in her thermal spray-coating research projects.

Transcript

MARGARET HYLAND I think of a plasma as a gas where you’ve put energy into it, and you turn that gas into this mass of atoms, electrons and ionised atoms, and it has different properties from a gas.

Artificial plasmas are plasmas that we generate, so we choose what kind of energy we’re going to put into it, what kind of a gas we’re going to ionise or convert to a plasma, and we do that because we want certain properties from that plasma. We might want it to be in a certain temperature range. We might want it to give off light in a certain way, like a fluorescent lamp, for example.

The artificial plasmas that I’m interested in are thermal plasmas, and they’re typically generated using high voltage, and they have temperatures in the tens of thousands of kelvin

We use them to heat something that has a really high melting point to its melting point or beyond. I use them to help deposit thermal spray-coatings, and we have a plasma gun.

So we generate a plasma – we have a plasma gas which we’re using – sometimes it’s helium, sometimes it’s argon, mixtures of those. And then into that we’re also shooting particles of the material that we want to make our coating from. And as they pass through the plasma, they get heated up, they melt and then they get shot towards a target, which we call a substrate. That is the material that we want to be coated.

Acknowledgements: Professor Margaret Hyland, Department of Chemical and Materials Engineering, University of Auckland Dr Steven Matthews Aaron Martin, Holster Engineering Ltd, Tokoroa Plasma ball photo is the copyrighted property of 123RF Limited, their contributors or licensed partners and is being used with permission under licence. This photo may not be copied or downloaded without permission from 123RF Limited. Still of fluorescent light tubes, courtesy Dmitry G, Creative Commons Licence 3.0 Still of plasma cutting torch, courtesy Loffredo, Creative Commons Licence 3.0 Patrick Reynolds, Philips Lighting NZ Schematic of plasma spray gun, courtesy Rudolfensis, Creative Commons Licence 3.0