Rights: The University of Waikato Published 9 April 2010 Download

Sialon is an acronym for silicon, aluminium, oxygen and nitrogen. In this video, IRL’s Dr Ian Brown explains how this new family of advanced ceramics are made and discusses some of their physical properties. He then goes on to explain how subtle changes in the formulation can allow sialons to be made with properties that fit a particular product or market.

Point of interest
What types of properties would a sialon need that is made to service the body armour market?

Adrian Hape
Bill F18E777
John Murphy
Isbi Armor


Sialons are a really interesting new family of materials. The word sialon – s-i-a-l-o-n – is just simply a cheat acronym for silicon, aluminium, oxygen and nitrogen. What it tells you is that you've got elements of a traditional silicon-aluminium-oxygen structure in your material, but you've introduced nitrogen into the chemical structure of this new ceramic, and it’s the nitrogen that makes all the difference in terms of the properties that we seek. We can change the ratios of those 4 elements to tune the properties.

So sialon itself is not one single material – it’s a whole raft of substituted phases with different formulations. Some of these materials are known for their thermal resistance, some are known for their extreme hardness, some are known for their extreme toughness, so depending on which sialon you choose to make, you can point the properties at a particular product or market. That’s the attraction of them.

So for light-weight body armour is something that has been developing over the last 10 or 15 years. Even simple materials like the alumina are used quite commonly in commercial ceramic body armour. Alumina ceramic body armour has a density of close to about 4 grams per cubic centimetre. That doesn't sound a lot, but if you actually pick up an A4 slab exercise book piece of alumina ceramic, that is a heavy item.

This is where our expertise in sialon ceramic research has come to the fore, because intrinsically, sialon has a density of about 3. So we figure that if we can develop materials of comparable performance, we should be able to reduce the weight of ceramic body armour by some 25%, and that is our goal, and that is what we are working to at this moment.