I need to thermally insulate two metal (say aluminum) parts, the first of which is at 200-400 °C (473-673 K), and the second one is at room temperature. It should be possible to screw the parts together or something, to form one solid assembly. The typical dimensions are like 10-40 mm. The insulator should be able to be created in a DIY setting.
The insulation material has to be reasonably stiff/strong to enable a rigid compound construction, so all plastic foams etc. are out and, due to the high temperatures, almost all (easily available) solid plastics are also out.
Comparing thermal conductivities I have found that all mineral-based materials are reasonably insulating at ~1 W/(mK) when compared to metals (~10^2 W/(mK)).
What has come to my mind (in order of ideation):
- fine-grained concrete
Anything obvious I have missed?
Gypsum seems very practical in that it can be easily cast with very fine structures. However I am not so sure whether it resists the heat (crystal water? gets more brittle at higher temp?). Anyway it is certainly a bad material for threading a metal screw in.
Glass is stiff and temperature resistant, but it is also sensitive to high temperature gradients and breaks easily under mechanic stress.
Fine-grained concrete (don't know if this exists at all as a product) - probably similar to gypsum, but a little stronger. But the question remains, if it can resist repeated heating/cooling/dehydration.
Porcelain (or other sintered minerals): sounds perfect, but can I reasonably expect to create a shaped part with threads/holes etc. at home?
Are there any best industry practices for parts like that?