🚀 go-pugleaf

In sci.materials, parks@gibbs.physics.purdue.edu (Chris Parks) writes:


>What is a good material (good=price + availability) which is
>an electrical insulator and a good conductor of heat?

>It will be used at temperatures as low as 4.2 Kelvin and it needs
>to hold up to about 200 volts / mm, heat conductivity needs to
>be comparable to copper.  Does it exist?

>Note: Diamond may be ideal but not practical!

>Chris Parks
>parks@physics.purdue.edu

Don't know about conditions at cryogenic temperatures, but assuming that
the heat conductivity is not that far from what it is at room temp
then ceramics such as aluminum nitride and beryllium oxide have very
respectable heat transfer. Certainly almost any insulator will be much 
better than 200 V/mm, so that part is easy.

If you can deal with much less thermal conductivity then you could consider
common alumina (~1/5 thermal cond of copper) or sapphire.

Too bad you can't use diamond.

Stay away from plastics and glasses and rubbers and the like- all are
very poor conductors.

I would suggest a very thin layer of good thermally conductive insulator
then a metal for the bulk of the application. This is standard in
the electronics industry, with one common and cheap solution being
anodized aluminum. This would have one major advantage in that aluminum
IS very good structurally at cryogenic temps.

Stan Bischof
SRSD