Alumina aerogel as refractory material

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In summary, the person is interested in building a forge for flux crystallization of corundum (ruby/sapphire) with the ability to withstand temperatures up to 1400 C for long periods, have walls with a thermal resistance of at least 1 m2*K/W, use electrical resistance heaters, and be somewhat air-tight for manipulation of furnace atmosphere. They are considering lining the furnace with several inches of Al2O3 aerogel for insulation, which is the only suitable material they have found that would not require walls to be 4+ feet thick. However, they have concerns about the aerogel's insulation value at high temperatures based on research from a paper on the properties of Al2O3 aerogel.
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yrtsimehc
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I'm interested in building a forge, mainly for flux crystallization of corundum (ruby/sapphire), but I want it to be versatile.

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
  • 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

Al2O3 has good thermal properties for my application, and I'm looking at lining my furnace with several inches of Al2O3 aerogel for use as insulation.

In fact, this 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.

Any thoughts on the suitability of aerogel as forge insulation, or on my plans in general?
 
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Forgot to include this link:

https://e-reports-ext.llnl.gov/pdf/242911.pdf

In this paper, the authors tested the properties of the al2o3 aerogel they synthesized, but not much over 1000 C. They mention that some sintering did occur at the upper bounds, which has me concerned that exposure to very high temperatures would reduce the aergoel's insulation value after several duty cycles.
 

FAQ: Alumina aerogel as refractory material

1. What is alumina aerogel?

Alumina aerogel is a highly porous, lightweight, and low-density material made from aluminum oxide, commonly known as alumina. It is created by removing the liquid component from a gel through a process called supercritical drying.

2. What makes alumina aerogel a good refractory material?

Alumina aerogel has excellent insulating properties, with a thermal conductivity of only 0.015 W/mK, making it a highly effective barrier against heat transfer. It also has a high melting point of 2040°C, making it suitable for use in high-temperature applications.

3. What are the advantages of using alumina aerogel as a refractory material?

Alumina aerogel is lightweight, with a density of only 0.003 g/cm³, making it easier to handle and install compared to traditional refractory materials. It also has a low thermal mass, allowing for faster heating and cooling cycles, reducing energy consumption and costs. Additionally, it is chemically inert, non-toxic, and has high corrosion resistance.

4. What are the potential applications of alumina aerogel as a refractory material?

Alumina aerogel can be used in a wide range of high-temperature applications, such as furnace linings, kiln insulation, and heat shields for aerospace and automotive industries. It can also be used in cryogenic environments, as it has a low thermal conductivity and can withstand extreme temperature changes.

5. How does the cost of alumina aerogel compare to other refractory materials?

Alumina aerogel is more expensive than traditional refractory materials, such as ceramic fiber or silica insulation, due to the complex manufacturing process and the high purity of alumina required. However, its superior insulating properties and long-term durability can result in cost savings in the long run, especially in high-temperature and energy-intensive applications.

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