Rocket Stove Materials

Would I be able to use metal ductwork as my core parts or would it not hold up to the heat? Im just planning on doing an outdoor rocket stove that would be mostly buried in the ground and probably supplemented with Cob above ground. Id like to turn it into a multiuse heat source for baking, cooking, drying etc. Cheers.

Becarefull with ductwork. It's not "Heat Resistant" and it can produce dangerious gass'es from the metal it's self when it's over heated.

Any suggestions on an alternative for the heat riser portion? My original thought was just to make one J shaped single piece stove and bury it under ground. If I cant use the metal ductwork, I would need something that would give me the same affect. I can't think of anything off the top of my head except for cast iron piping, which would probably be overkill. Thanks for your input

How about clay chimney tiles, use chimney blocks and pour vermiculite between the blocks and tile for insulation, then cob the outside (just a thought). I built a rocket out back (just to prove to people around here they actually work) and used the blocks from a chimney I tore down (it was tear down or fall down) with no insulation or liner, worked the ball's after I got enough heat rolling up through it (about an hour of fire play), figured a tile and some insulation would improve the fire play time (a work in progress!).

That sounds like a good idea, I was just hoping to do something a little less time consuming and cheaper. Do they even sell fire resistant materials at like a home depot/lowes etc. ?