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Specialty Chemistry Forums => Materials and Nanochemistry forum => Topic started by: Sylar on March 05, 2013, 01:07:16 PM

Title: Alumina aerogel as refractory material
Post by: Sylar on March 05, 2013, 01:07:16 PM
I'm interested in building a forge, mainly for playing around with flux crystallization of corundum (ruby/sapphire), but I want it to be versatile for other things I might want to do in the future.

General Requirements:

    Withstand temperatures up to 1400 C (2550 F) for months at a time (crystallization can have very slow kinetics)
    Walls with a thermal resistance of at least 1 m2*K/W (otherwise I'd be spending tens of thousands of dollars to keep the furnace at temperature)
    Electrical resistance heaters (MoSi2 or other)
    Somewhat air-tight to allow for manipulation of furnace atmosphere through gas injection
    Interior volume of ~8 cubic feet


Aerogel is pretty much the only suitable material I've found that will give my furnace walls an acceptable thermal resistance without having to have walls that are 4+ feet thick. I'm concerned that at high temperatures the aerogel might sinter and after several duty cycles, might degrade as thermal insulation. My concerns come from this paper: https://e-reports-ext.llnl.gov/pdf/242911.pdf

Any thoughts on the suitability of aerogel as forge insulation, or on my plans in general?
Title: Re: Alumina aerogel as refractory material
Post by: billnotgatez on March 05, 2013, 03:01:52 PM
So you are building something like this

http://carbolite.thomasnet.com/item/furnaces-box-furnaces/-1500-176c-1600-176c-high-temperature-box-furnaces/rhf-15-3?&bc=100|1001|1004|3001002|3001004|3001005|3001006

http://www.carbolite.us/
Title: Re: Alumina aerogel as refractory material
Post by: Sylar on March 05, 2013, 03:45:03 PM
Yes, very similar to that.

Obviously, for my needs slow warm-up would be almost irrelevant and reducing power consumption would be my top priority.

Does anyone have experience with aerogels? They seem kind of finicky and time-consuming to make, what with all the solvent exchanging, but if I built a supercritical dryer with a large chamber, it wouldn't take a prohibitively long time to make 8 cubic feet of aerogel.