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Rights: The University of Waikato
Published 9 April 2010

In this video, Dr Ian Brown explains how his materials research team at IRL developed an oxygen-rich sialon called O-Sialon. The excellent thermal shock resistance properties allied to high oxidation resistance have resulted in this advanced ceramic being used to fabricate refractories for use in the aluminium industry.

Points of interest
What is the melting point of aluminium?
How is aluminium produced?



O-Sialon as opposed to sialon itself is, I guess as the name indicates, it’s an oxygen-enriched sialon so it has a little less nitrogen, a little more oxygen. And what that does is it makes the material somewhat more oxidation-resistant. So if you are going to use a material at high temperature, you want your ceramic not to be damaged by the oxygen environment you're going to fire it in, but to actually resist that, and O-Sialons do just that. They are thermally shock-resistant materials, and they are very resistant to high-temperature oxidation.

We were very familiar with the material O-Sialon, and we knew what it did, and we knew that it would actually meet out needs for the particular application for high-temperature materials for refractory use in the aluminium industry, but the only ways that we could see how to manufacture this material were from quite expensive individual components that, while it’s great to do this in a lab, you can't afford that if you're running a commercial business.

There was a key development made by our research team – a controlled accident, I think, is the best way to describe this, like a lot of science is. We tried and tried to make this work and to make it sort of more fluid because we were trying to cast this thing. We wanted a plasticiser, and then we thought a bit of clay will do the job for plasticising this. We put the clay material in, it worked, we analysed the material and suddenly found that we had a new phase present. And we thought, ah, if we put more clay mineral in, we will get more of this new phase, and in the end, we decided that we were able to develop the O-Sialon from classical raw materials such as clay minerals and silica and then some elemental silicon metal.

And so a carefully worked out blend of those 3 things gave us, in 1 step, at 1,450 degrees an O-Sialon, which is a process that we have patented in conjunction with our industry partners, and it’s a process that we have developed from fundamentally teaspoon scale sized samples in the lab, right through to full commercial production with our business partner.