Stainless, superalloys, or other??

[paulengr]

One more tidbit I almost totally forgot about.

In the refractory business, the term "refractory" refers to materials which by nature are highly abrasion resistant. Insulative means...well, you can probably guess.

There are three other properties that are also key at least industrially. Wettability is one...if you are dealing with liquids and the ceramic has a tendency to more or less soak up the liquid like a sponge...well, that's bad. It has a tendency to destroy the insulative properties of the material. Generally, they use very refractory (ie, DENSE) materials in areas with a lot of liquids present because they last longer. In addition to that though, even refractories have wettability properties. I mean...consider how waxed paper acts when you put a drop of water on it...it beads up and rolls off. If it's oil, it smears out and tends to soak in. Same thing with refractories and certain materials. ZrO2 is great in this respect with the way it reacts towards slags and cements. It lasts for a very long time in the cooler areas of the kiln.

Second, there is pH. MgO is a "basic" material. It works well with high pH materials such as cement and especially lime.

Some glasses, sulfide ores (copper smelters come to mind) and most metallurgical slags on the other hand are very acidic. In this environment, MgO would be a waste of time since it would be rapidly dissolved. Blocks of pure graphite are commonly used in the worst areas, and there are a few other materials (acid resistance is a bit of an issue in refractories).

Finally, there's density. It's great to be able to go with a super lightweight refractory for insulation purposes. Simple mill board and spun materials are awesome insulators but they can't tolerate any kind of abuse whatsoever. "Spun" means fiberglass and then eventually spun kaolin (kao-wool or some dolomite rock wools) which can tolerate up to over 3000 F without any trouble.

BUT it can't be crushed or smacked around for much of any time. So then you have to go with castables, "plastics", and eventually only brick.

[Mark]

The tiles are described best towards the bottom of the article I think.
Mark
http://en.wikipedia.org/wiki/Space_shut ... ion_system