Does anyone know if you can buy the emission reducing material found inside of a CAT on it's own?

Also is it a rigid material or can it be rolled/re-shaped to a different size?

It is a rigid foamy type of thing. Platinum is coated over it, and it may not travel well unprotected.
There are a few places who produce motorsport catalysts, must be a better idea than trying to make one?

It is a rigid very hard brittle ceramic honeycomb with a very fine surface coating with particles of the catalytic material.

looking at some of the ones I have bought, there are types that appear to be made from a wound corrogated sheet rather than the orginal solid blocks. Not that I have dismantled one before but it did look like it was a flexable material. If you are tight for space some are quite small like my Zafira's that is only about 4 inch's in diameter.

This is the kind of core I have seen, to me this is made of sheet material -







[Edited on 17/8/11 by Mr Whippy]

My MR2 had a big spiral sheet of corrugated "stuff". However, it wasn't very flexible, bending it would snap it.

You'll probably find they're hot formed.

The one in my 3sgte was/is a solid honeycomb. No idea what the one in the renault was but it got rattled about and spat out fairly quickly in normal use, so I'd say cheese.

There are basically two types. The one used by most oem's is a Ceramic type, which is easily damaged but relatively cheap to manufacture and the second much more durable but more expensive type is the metal substrate, used in high performance/motorsport applications. This one comes in several densities.

I purchase my blanks from Blackthorn. You can find more info regarding the different substrates on their website
http://www.blackthorn.eu.com/html/catalytic-converters-substrates.aspx

[Edited on 18/8/11 by atomic]