Rights: The University of Waikato Published 9 April 2010 Download

There are numerous challenges that materials scientists like IRL’s Dr Ian Brown face in the development of novel advanced ceramics. In this video, Ian describes the main challenges often encountered. The first and most critical challenge is to blend the starting ingredients as near to a molecular level as possible. Another challenge centres on the capability of the high-temperature furnace.

Point of interest
Clay ceramics fire perfectly well in air atmospheres. Advanced ceramics like O-Sialons do not. Why is this?


There’s a lot of challenges involved in advanced ceramic research and development. It starts out right from the very first principles of sufficiently and uniformly and thoroughly blending together all the raw materials as near to a molecular level as you can possibly get, because what you are trying to do is set up what we call a microstructure, that is, the ways the little grains of material sit with respect to one another. So by having these individual grains or particles of our ceramic minerals or materials very very fine, very thoroughly interblended, then we set ourselves up for the best way of moving forward.

So how are we going to hold these things together? Because some of these materials we are talking about don't have clay in them, and if you are talking about a traditional ceramic body, it’s got clay in it, and that acts like a sort of a soft wet glue that sticks all the materials together so you can mould it and shape it and pick it up and put it on a shelf and dry it off and so forth. You don't necessarily have that luxury or that ability with an advanced ceramic, so something else often has to fit the bill.

We have to get these powders into a condition where we can bind them together in the unfired or green state, so we call this a ‘green body’. It hasn't been fired yet, so the real trick here is to get these materials shaped to the best possible green density and as near their final shape as possible. That way, we do less work when we fire.

When you fire, of course, things shrink. Ceramics shrink when they are fired, and whether they are a traditional clay-based body or a high-performance advanced ceramic, they still shrink when they are fired. We have to control that shrinkage. You risk losing some of the structural integrity of this because it might warp or distort.

Talking about furnaces, there’s one of the other challenges for high-performance or advanced ceramics that, more often than not, we are talking about really high-temperature furnaces that may need to go to 1,800 degrees or even higher. One of our laboratory furnaces will go to over 2,000 degrees if we need to use that.

We are also talking about using controlled atmospheres. We can't fire many of these materials in a straight open-air atmosphere. The really important thing is to get rid of the oxygen from the firing atmosphere so we can synthesise and densify these nitrogen ceramics without damage.